Question

ax + by = a-b and bx-ay=a+b solve for it

Answer 1

AX+by = a-b 
and bx-ay=a+b
than solve
ax-by=a-b
bx-ay=a+b
-   +    -  -
ax-bx-by+ay=-2b
x(a-b)+y(a-b) =-2b
(x+y)(a-b)=-2b

Answer 2

Hi. Refer to the attachment for the answer.