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# An Extra Unknown Factor 1

SATMAT-YULY5T

If $\frac { 1 }{ 2 } a + \frac { 3 }{ 4 } b = 10$, and $k\left( \frac { 1 }{ 2 } a + \frac { 3 }{ 4 } b \right) =15$, then what is the value of the constant $k$?

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A

$5$

B

$\cfrac { 3 }{ 2 }$

C

$2$

D

$\cfrac { 1 }{ 2 }$