Question

Find the values of $(x+y)$ and $(x-y)$without actually solving for $x$ and $y$.$15x-12y=69;12x-15y=39$

• A. $x+y=10,x-y=4$
• B. $x+y=5,x-y=4$
• C. $x+y=13,x-y=4$
• D. $x+y=19,x-y=4$

Answer 1

Answer: (A)

$x+y=10,x-y=4$

$15x-12y=69$ ...(i)

$12x-15y=39$ ...(ii)

On adding (i) and (ii) , we get

$27x-27y=108$

$\Rightarrow x-y=4$

On subtracting (ii) from (i) , we get

$3x+3y=30$

$\Rightarrow x+y=10$