Question

Difficulty: HardLinear Equations in One Variable
If xx satisfies the linear equation
2(3x−1)5−4x−33=x+1815−2\frac{2(3x - 1)}{5} - \frac{4x - 3}{3} = \frac{x + 18}{15} - 2
what is the value of 3x−53x - 5?
  1. A
    77
  2. 1616Answer
  3. C
    −14-14
  4. D
    −12-12
  5. E
    4040

Answer

16
Multiplying the entire equation by the common denominator 1515 clears all fractions, yielding 6(3x−1)−5(4x−3)=(x+18)−306(3x - 1) - 5(4x - 3) = (x + 18) - 30. Expanding both sides produces 18x−6−20x+15=x−1218x - 6 - 20x + 15 = x - 12, which simplifies to −2x+9=x−12-2x + 9 = x - 12. Rearranging terms yields −3x=−21-3x = -21, so x=7x = 7. Substituting x=7x = 7 into 3x−53x - 5 gives 3(7)−5=163(7) - 5 = 16.

Step-by-Step Solution

1
Clear the denominators by multiplying both sides of the equation by the least common multiple (LCM) of 5, 3, and 15, which is 15.
15⋅(2(3x−1)5)−15⋅(4x−33)=15⋅(x+1815)−15⋅215 \cdot \left(\frac{2(3x - 1)}{5}\right) - 15 \cdot \left(\frac{4x - 3}{3}\right) = 15 \cdot \left(\frac{x + 18}{15}\right) - 15 \cdot 2
Eliminating fractions simplifies the linear equation into standard integer polynomial terms.
2
Simplify the products and distribute coefficients across parentheses.
3⋅2(3x−1)−5(4x−3)=(x+18)−30  ⟹  6(3x−1)−5(4x−3)=x−123 \cdot 2(3x - 1) - 5(4x - 3) = (x + 18) - 30 \implies 6(3x - 1) - 5(4x - 3) = x - 12
Perform fractional reduction and simplify constants on the right side.
3
Expand both groupings and combine like terms on the left-hand side.
18x−6−20x+15=x−12  ⟹  −2x+9=x−1218x - 6 - 20x + 15 = x - 12 \implies -2x + 9 = x - 12
Ensure the negative sign is properly distributed to both terms inside −5(4x−3)-5(4x - 3).
4
Isolate the variable xx by subtracting xx and 99 from both sides.
−3x=−21  ⟹  x=7-3x = -21 \implies x = 7
Solve for the single variable xx.
5
Substitute x=7x = 7 into the target expression 3x−53x - 5.
3(7)−5=21−5=163(7) - 5 = 21 - 5 = 16
The question asks for the value of the algebraic expression 3x−53x - 5, not xx alone.

Key Concept

Linear Equations in One Variable with Fractional Coefficients
Estimated Time:2m 0s
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