Solve Linear Equation: 3(b-1)-4(-b+3)=-28 Step by Step

Linear Equations with Mixed Fractions

3(b1)4(b+3)=28 3(b-1)-4(-b+3)=-28

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 Open parentheses properly, multiply by each factor
00:14 Collect terms
00:23 Arrange the equation so that only the unknown B is on one side
00:31 Use long subtraction to calculate
00:39 Isolate B
00:44 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

3(b1)4(b+3)=28 3(b-1)-4(-b+3)=-28

2

Step-by-step solution

To solve the given equation 3(b1)4(b+3)=283(b-1)-4(-b+3)=-28, let's follow these steps:

  • Step 1: Distribute the constants.
  • Step 2: Simplify by combining like terms.
  • Step 3: Isolate the variable bb.

Now, let's work through each step:
Step 1: Apply the distributive property.
Starting with 3(b1)4(b+3)3(b-1)-4(-b+3), distribute the constants:
3(b)+3(1)4(b)43=3b3+4b12 3 \cdot (b) + 3 \cdot (-1) - 4 \cdot (-b) - 4 \cdot 3 = 3b - 3 + 4b - 12

Step 2: Combine like terms.
Combine the terms involving bb and the constant terms:
3b+4b312=7b15 3b + 4b - 3 - 12 = 7b - 15
Set this equal to the right side of the equation:
7b15=28 7b - 15 = -28

Step 3: Solve for bb.
Add 15 to both sides to isolate the term with bb:
7b=28+15 7b = -28 + 15

This simplifies to:
7b=13 7b = -13

Finally, divide both sides by 7 to solve for bb:
b=137 b = \frac{-13}{7}

Therefore, the solution to the problem is b=167 b = -1\frac{6}{7} .

Reviewing the answer choices, our solution b=167 b = -1\frac{6}{7} matches the correct answer choice.

3

Final Answer

167 -1\frac{6}{7}

Key Points to Remember

Essential concepts to master this topic
  • Distribution Rule: Apply distributive property to both positive and negative terms
  • Sign Technique: -4(-b) becomes +4b because negative times negative equals positive
  • Check Work: Substitute b=167 b = -1\frac{6}{7} back into original equation ✓

Common Mistakes

Avoid these frequent errors
  • Incorrect sign handling during distribution
    Don't forget to change signs when distributing negative numbers = wrong coefficients! Many students write -4(-b) as -4b instead of +4b, leading to 3b - 15 = -28 instead of 7b - 15 = -28. Always remember that negative times negative equals positive.

Practice Quiz

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\( 5x=1 \)

What is the value of x?

FAQ

Everything you need to know about this question

Why does -4(-b+3) become +4b-12?

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When you distribute -4 to each term inside the parentheses: -4 × (-b) = +4b (negative times negative is positive) and -4 × 3 = -12. So -4(-b+3) = +4b - 12.

How do I convert -13/7 to a mixed number?

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Divide 13 by 7: 13 ÷ 7 = 1 remainder 6. So 137=167 -\frac{13}{7} = -1\frac{6}{7} . The negative sign goes in front of the whole mixed number.

What if I get a different answer when checking?

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Go back and check your distribution step first - that's where most errors happen! Make sure you handled all the negative signs correctly, especially with -4(-b+3).

Can I solve this without distributing first?

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It's much harder! You'd need to work with nested parentheses. Always distribute first to simplify the equation into standard form before combining like terms.

Why do we combine 3b and 4b to get 7b?

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These are like terms because they both contain the variable b. Just add their coefficients: 3 + 4 = 7, so 3b + 4b = 7b.

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