Question

Difficulty: HardLinear Equations in One Variable

If 25(3x4)13(2x+5)=15x+1115\frac{2}{5}(3x - 4) - \frac{1}{3}(2x + 5) = \frac{1}{5}x + \frac{11}{15}, what is the value of 2x72x - 7?

Answer: 17

Answer

The correct answer is 17.
To find the value of 2x72x - 7, first solve the linear equation for xx. Distributing the coefficients on the left side of the equation gives 65x8523x53=15x+1115\frac{6}{5}x - \frac{8}{5} - \frac{2}{3}x - \frac{5}{3} = \frac{1}{5}x + \frac{11}{15}. Combining the variable terms and constants on the left side results in 815x4915=315x+1115\frac{8}{15}x - \frac{49}{15} = \frac{3}{15}x + \frac{11}{15}. Subtracting 315x\frac{3}{15}x and adding 4915\frac{49}{15} to both sides yields 515x=6015\frac{5}{15}x = \frac{60}{15}, which simplifies to 13x=4\frac{1}{3}x = 4, or x=12x = 12. Finally, substituting 12 into the expression 2x72x - 7 gives 2(12)7=172(12) - 7 = 17.

Step-by-Step Solution

1
Distribute the coefficients to the terms inside the parentheses.
65x8523x53=15x+1115\frac{6}{5}x - \frac{8}{5} - \frac{2}{3}x - \frac{5}{3} = \frac{1}{5}x + \frac{11}{15}
To eliminate parentheses and allow grouping of like terms.
2
Combine the variable terms and the constant terms on the left side using a common denominator of 15.
815x4915=315x+1115\frac{8}{15}x - \frac{49}{15} = \frac{3}{15}x + \frac{11}{15}
To simplify the linear equation into a standard two-sided form.
3
Subtract the variable term from the right side and add the constant term from the left side.
515x=6015\frac{5}{15}x = \frac{60}{15}, which simplifies to x=12x = 12
To isolate the variable xx on one side of the equation.
4
Evaluate the expression 2x72x - 7 using the value of xx.
2(12)7=172(12) - 7 = 17
To solve for the final requested quantity.

Key Concept

Linear Equations in One Variable
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