Solve the Linear Equation: 7(x-4)+3=5-4(x+5) Step by Step

Linear Equations with Distributive Property

Solve for X:

7(x4)+3=54(x+5) 7(x-4)+3=5-4(x+5)

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:04 Make sure to open brackets properly, multiply by each factor
00:21 Solve each multiplication separately
00:27 Positive times negative always equals negative
00:42 Group terms
00:52 Arrange the equation so that one side has only the unknown X
01:12 Group terms
01:26 Isolate X
01:35 Simplify as much as possible
01:39 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:

7(x4)+3=54(x+5) 7(x-4)+3=5-4(x+5)

2

Step-by-step solution

Let's solve the given equation step by step:

We start with the equation:

7(x4)+3=54(x+5) 7(x-4) + 3 = 5 - 4(x+5)

Step 1: Apply the distributive property to eliminate the parentheses.

The left-hand side becomes:

7(x4)=7x28 7(x-4) = 7x - 28 , so the entire expression on the left is 7x28+3 7x - 28 + 3 .

The right-hand side becomes:

4(x+5)=4x20 -4(x+5) = -4x - 20 , so the whole right side is 54x20 5 - 4x - 20 .

Step 2: Simplify both sides.

Simplify the left-hand side:

7x28+3=7x25 7x - 28 + 3 = 7x - 25 .

Simplify the right-hand side:

54x20=4x15 5 - 4x - 20 = -4x - 15 .

Now the equation reads:

7x25=4x15 7x - 25 = -4x - 15 .

Step 3: Rearrange the equation to isolate x x terms on one side and constants on the other.

Add 4x 4x to both sides:

7x+4x25=4x+4x15 7x + 4x - 25 = -4x + 4x - 15 .

This simplifies to:

11x25=15 11x - 25 = -15 .

Step 4: Solve for x x .

Add 25 to both sides:

11x=10 11x = 10 .

Divide both sides by 11 to solve for x x :

x=1011 x = \frac{10}{11} .

Thus, the solution to the equation is x=1011 x = \frac{10}{11} .

Considering the given choices, the correct answer is choice 3: 1011 \frac{10}{11} .

3

Final Answer

1011 \frac{10}{11}

Key Points to Remember

Essential concepts to master this topic
  • Distributive Property: Multiply outside number by each term inside parentheses
  • Technique: Combine like terms: 7x + 4x = 11x when collecting variables
  • Check: Substitute x=1011 x = \frac{10}{11} back into original equation ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to distribute negative signs correctly
    Don't write -4(x+5) as -4x + 20 = wrong signs throughout! The negative distributes to both terms, making it -4x - 20. Always apply the negative sign to every term inside parentheses.

Practice Quiz

Test your knowledge with interactive questions

Solve for \( b \):

\( 8-b=6 \)

FAQ

Everything you need to know about this question

Why do I need to distribute first before combining like terms?

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You must eliminate parentheses first using the distributive property! If you try to combine terms while they're still in parentheses, you'll make errors. Always distribute, then simplify.

How do I handle the negative sign in front of parentheses?

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The negative sign acts like multiplying by -1. So -4(x+5) becomes (-4)(x) + (-4)(5) = -4x - 20. Each term inside gets multiplied by the negative.

What's the best way to keep track of positive and negative terms?

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Write each step clearly and use extra parentheses when needed. For example: 5 + (-4x) + (-20) = 5 - 4x - 20. This helps you see which terms are positive or negative.

Why did I get a fraction as my answer?

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Fractions are perfectly normal solutions to linear equations! x=1011 x = \frac{10}{11} means x is between 0 and 1, which is a valid solution. Always check if your fraction can be simplified.

How can I verify my answer is correct?

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Substitute x=1011 x = \frac{10}{11} back into the original equation 7(x4)+3=54(x+5) 7(x-4)+3=5-4(x+5) . If both sides equal the same number, your answer is correct!

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