Question

Subtract:

2a+b=7
-a+b=7​

Answer 1

$(2a + b) - ( - a + b) = 7 - 7 \\ 2a + b + a - b = 0 \\ 3a = 0 \\ a = 0$

So, putting value of a in first equation,

$2(0) + b = 7 \\ b = 7$

a = 0

b = 7

Hope It Helps :)