Solve the Rational Equation: (5+3(x-2))/(5+x) = 3/4

Rational Equations with Cross-Multiplication Method

Solve for X:

5+3×(x2)5+x=34 \frac{5+3\times(x-2)}{5+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
00:04 Multiply by the common denominator to eliminate fractions
00:19 Make sure to open parentheses properly, multiply by each factor
00:49 Combine like terms
00:59 Arrange the equation so that X is isolated on one side
01:10 Combine like terms
01:14 Isolate X
01:17 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:

5+3×(x2)5+x=34 \frac{5+3\times(x-2)}{5+x}=\frac{3}{4}

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Cross-multiply to eliminate the fractions.
  • Step 2: Simplify the resulting linear equation.
  • Step 3: Solve for x x .

Now, let's work through each step:

Step 1: Starting with the equation:

5+3×(x2)5+x=34\frac{5 + 3 \times (x - 2)}{5 + x} = \frac{3}{4}

Cross-multiply to remove the fractions:

4(5+3×(x2))=3(5+x)4 \cdot (5 + 3 \times (x - 2)) = 3 \cdot (5 + x)

Step 2: Simplify the equation. Expand inside the brackets:

4(5+3x6)=3(5+x)4 \cdot (5 + 3x - 6) = 3 \cdot (5 + x)

Simplify further:

4(3x1)=3(5+x)4 \cdot (3x - 1) = 3 \cdot (5 + x)

Distribute the constants:

12x4=15+3x12x - 4 = 15 + 3x

Step 3: Solve for x x .

Subtract 3x 3x from both sides:

12x3x4=1512x - 3x - 4 = 15

9x4=159x - 4 = 15

Add 4 to both sides:

9x=199x = 19

Divide both sides by 9:

x=199x = \frac{19}{9}

Therefore, the solution to the problem is x=199 x = \frac{19}{9} .

3

Final Answer

199 \frac{19}{9}

Key Points to Remember

Essential concepts to master this topic
  • Cross-Multiplication: When one fraction equals another, multiply diagonally across
  • Technique: ab=cd \frac{a}{b} = \frac{c}{d} becomes ad=bc ad = bc to eliminate fractions
  • Check: Substitute x=199 x = \frac{19}{9} back: both sides equal 34 \frac{3}{4}

Common Mistakes

Avoid these frequent errors
  • Forgetting to distribute after cross-multiplication
    Don't write 4(5 + 3(x - 2)) = 3(5 + x) and then skip the distribution steps = wrong simplified equation! Students often cross-multiply correctly but fail to expand the parentheses properly. Always distribute each multiplied term completely: 4(5 + 3x - 6) becomes 4(3x - 1) = 12x - 4.

Practice Quiz

Test your knowledge with interactive questions

Solve for X:

\( 6 - x = 10 - 2 \)

FAQ

Everything you need to know about this question

Why can I cross-multiply here but not always?

+

Cross-multiplication works only when you have exactly one fraction on each side of the equals sign. Since we have 5+3(x2)5+x=34 \frac{5+3(x-2)}{5+x} = \frac{3}{4} , we can cross-multiply safely!

What if I mess up the distribution step?

+

Take it one step at a time! First expand 3(x2)=3x6 3(x-2) = 3x - 6 , then 5+3x6=3x1 5 + 3x - 6 = 3x - 1 . Double-check each arithmetic step before moving on.

How do I know if x = 19/9 is really correct?

+

Substitute back into the original equation! Calculate 5+3(1992)5+199 \frac{5+3(\frac{19}{9}-2)}{5+\frac{19}{9}} and verify it equals 34 \frac{3}{4} . If both sides match, you're right!

Can I convert 19/9 to a decimal instead?

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You can, but fractions are often more exact! 199 \frac{19}{9} is the precise answer, while 2.111... is rounded. Keep fractions when possible.

What if the denominator 5+x equals zero?

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Great question! If 5+x=0 5 + x = 0 , then x=5 x = -5 makes the fraction undefined. Since our answer is 199 \frac{19}{9} , we're safe!

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