Solve for X in (5+3x)/x = 3/4: Rational Equation Solution

Cross-Multiplication with Rational Expressions

Solve for X:

5+3xx=34 \frac{5+3x}{x}=\frac{3}{4}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:03 Multiply by denominators to eliminate fractions
00:22 Simplify as much as possible
00:31 Carefully open parentheses properly, multiply by each factor
00:48 Arrange the equation so that one side has only the unknown X
01:06 Collect like terms
01:14 Isolate X
01:21 Simplify as much as possible
01:24 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve for X:

5+3xx=34 \frac{5+3x}{x}=\frac{3}{4}

2

Step-by-step solution

Let's solve the equation 5+3xx=34\frac{5+3x}{x} = \frac{3}{4}.

  • Step 1: Begin by applying cross-multiplication to eliminate the fractions. This gives us:

(5+3x)4=3x(5 + 3x) \cdot 4 = 3 \cdot x
Simplifying, we get:
20+12x=3x20 + 12x = 3x

  • Step 2: Rearrange the equation to bring all terms involving xx to one side:

20+12x3x=020 + 12x - 3x = 0
Simplifying, we find:
20+9x=020 + 9x = 0

  • Step 3: Isolate xx by solving the equation:

9x=209x = -20
Divide both sides by 9 to solve for xx:
x=209x = -\frac{20}{9}

Therefore, the solution to the equation 5+3xx=34\frac{5+3x}{x} = \frac{3}{4} is x=209x = -\frac{20}{9}.

3

Final Answer

209 -\frac{20}{9}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Cross-multiply when equation has one fraction on each side
  • Technique: (5+3x)×4 = 3×x gives 20+12x = 3x
  • Check: Substitute x=209 x = -\frac{20}{9} back into original equation ✓

Common Mistakes

Avoid these frequent errors
  • Distributing incorrectly after cross-multiplication
    Don't write 4(5+3x) as 4×5 + 3x = 20+3x! This misses multiplying 4 by the 3x term, giving wrong coefficients. Always distribute to every term: 4(5+3x) = 4×5 + 4×3x = 20+12x.

Practice Quiz

Test your knowledge with interactive questions

Solve for X:

\( x - 3 + 5 = 8 - 2 \)

FAQ

Everything you need to know about this question

Why can I cross-multiply in this equation?

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You can cross-multiply because you have one fraction equal to another fraction. When ab=cd \frac{a}{b} = \frac{c}{d} , then a×d = b×c. This eliminates both denominators at once!

What if x is in the denominator like this problem?

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Be careful! Since x is in the denominator, x cannot equal zero (division by zero is undefined). Always check that your final answer doesn't make any denominator zero.

Do I need to worry about x = 0 in this problem?

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Yes! Since our answer is x=209 x = -\frac{20}{9} , which is not zero, we're safe. But always remember to check that your solution doesn't make the original equation undefined.

How do I handle the fraction in my final answer?

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The fraction 209 -\frac{20}{9} is already in lowest terms since 20 and 9 share no common factors. Keep it as a fraction - don't convert to decimal unless specifically asked!

Can I check my answer without substituting back?

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Always substitute back! It's the most reliable way to catch errors. When you substitute x=209 x = -\frac{20}{9} , both sides should equal 34 \frac{3}{4} .

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