How to solve x-y=102x-y=17

X-y=10

2x-y=17

So to start

x=10+y

now replace x in the second equation

2 (10+y) - y=17

20+2y-y=17

20+y=17

y=17-20

y=-3

Now replace y with - 3 in any equation to find x

x - (-3) = 10

x+3=10

x=10-3

x=7