Solve for X in the Fraction Equation: Isolate the Variable Step-by-Step

Linear Equations with Mixed Fractional Terms

Solve for X:

15(x+14)=710+35x25 -\frac{1}{5}(x+\frac{1}{4})=\frac{7}{10}+\frac{3}{5}x-\frac{2}{5}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:03 Open parentheses properly, multiply by each factor
00:20 Find the common denominator and multiply accordingly
00:52 Arrange the equation so that only the unknown X is on one side
01:07 Collect like terms
01:13 Isolate X
01:20 And this is the solution to the problem

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve for X:

15(x+14)=710+35x25 -\frac{1}{5}(x+\frac{1}{4})=\frac{7}{10}+\frac{3}{5}x-\frac{2}{5}

2

Step-by-step solution

To solve this linear equation, we begin by simplifying it:

Step 1: Distribute the fraction on the left side of the equation.

  • We have 15(x+14)-\frac{1}{5}(x + \frac{1}{4}). Distribute the 15-\frac{1}{5}:
    15x1514=15x120 -\frac{1}{5} \cdot x - \frac{1}{5} \cdot \frac{1}{4} = -\frac{1}{5}x - \frac{1}{20} So, the equation becomes:
    15x120=710+35x25 -\frac{1}{5}x - \frac{1}{20} = \frac{7}{10} + \frac{3}{5}x - \frac{2}{5}

Step 2: Simplify the right side.

  • First, combine the constant terms 710\frac{7}{10} and 25-\frac{2}{5} on the right side:
    Convert 25-\frac{2}{5} to tenths to combine: 25=410-\frac{2}{5} = -\frac{4}{10}.
    Now, 710410=310\frac{7}{10} - \frac{4}{10} = \frac{3}{10}.
    The right side simplifies to:
    310+35x \frac{3}{10} + \frac{3}{5}x

Step 3: Move all terms involving x x to one side and constants to the other.

  • Add 15x\frac{1}{5}x to both sides:
    120=310+35x+15x -\frac{1}{20} = \frac{3}{10} + \frac{3}{5}x + \frac{1}{5}x
  • Combine like terms involving x x on the right side:
    Convert 15x\frac{1}{5}x to a common denominator with 35x\frac{3}{5}x which is 35x=610x \frac{3}{5}x = \frac{6}{10}x and 15x=210x\frac{1}{5}x = \frac{2}{10}x, giving us:
    810x \frac{8}{10}x , thus yielding
    310+810x \frac{3}{10} + \frac{8}{10}x
  • To isolate x x , subtract 310\frac{3}{10} from both sides:
    120310=810x -\frac{1}{20} - \frac{3}{10} = \frac{8}{10}x

Step 4: Solve the resulting equation for x x .

  • Calculate 120310-\frac{1}{20} - \frac{3}{10}:
    Convert 310-\frac{3}{10} to a common denominator with 120-\frac{1}{20}:
    310=620-\frac{3}{10} = -\frac{6}{20}.
    So, 120620=720-\frac{1}{20} - \frac{6}{20} = -\frac{7}{20}:
    The equation becomes:
    720=810x -\frac{7}{20} = \frac{8}{10}x
  • Divide both sides by 810\frac{8}{10} to solve for x x :
    x=(720)÷(810) x = \left(-\frac{7}{20}\right) \div \left(\frac{8}{10}\right)
  • When dividing fractions, invert the divisor and multiply:
    x=720×108 x = -\frac{7}{20} \times \frac{10}{8}
  • Simplify:
    x=7×1020×8=70160 x = -\frac{7 \times 10}{20 \times 8} = -\frac{70}{160}
  • Simplify further by dividing both numerator and denominator by the greatest common divisor (which is 10):
    x=716 x = -\frac{7}{16}

Therefore, the solution to the equation is x=716 x = -\frac{7}{16} .

The correct choice is:

716 -\frac{7}{16}

3

Final Answer

716 -\frac{7}{16}

Key Points to Remember

Essential concepts to master this topic
  • Distribution: Apply negative fraction to all terms inside parentheses
  • Technique: Convert 35x+15x=45x \frac{3}{5}x + \frac{1}{5}x = \frac{4}{5}x using common denominators
  • Check: Substitute x=716 x = -\frac{7}{16} back into original equation ✓

Common Mistakes

Avoid these frequent errors
  • Incorrectly combining fractions with different denominators
    Don't add 35x+15x=410x \frac{3}{5}x + \frac{1}{5}x = \frac{4}{10}x without converting! This gives wrong coefficients and incorrect final answers. Always convert fractions to common denominators before combining: 35x+15x=45x \frac{3}{5}x + \frac{1}{5}x = \frac{4}{5}x .

Practice Quiz

Test your knowledge with interactive questions

\( x+x=8 \)

FAQ

Everything you need to know about this question

Why do I need to distribute the negative fraction first?

+

The distributive property requires you to multiply 15 -\frac{1}{5} by each term inside the parentheses. If you skip this step, you'll have the wrong equation to solve!

How do I combine fractions with variables when denominators are different?

+

Convert to a common denominator first! For example: 35x=610x \frac{3}{5}x = \frac{6}{10}x and 15x=210x \frac{1}{5}x = \frac{2}{10}x , so they add to 810x \frac{8}{10}x .

What's the easiest way to subtract fractions like 7/10 - 2/5?

+

Convert to the same denominator: 25=410 \frac{2}{5} = \frac{4}{10} , so 710410=310 \frac{7}{10} - \frac{4}{10} = \frac{3}{10} . Always use the LCD!

When I divide by a fraction, do I really flip and multiply?

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Yes! Dividing by 810 \frac{8}{10} means multiplying by 108 \frac{10}{8} . So 720÷810=720×108 -\frac{7}{20} ÷ \frac{8}{10} = -\frac{7}{20} \times \frac{10}{8} .

How do I know when to simplify my final answer?

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Always simplify fractions to lowest terms! For 70160 -\frac{70}{160} , divide both numerator and denominator by 10 to get 716 -\frac{7}{16} .

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