How do u do 2x-y=17

X-y=10

Multiply (x-y=10) by - 2. You will get - 2x+2y=-20. then multiply by 1 2x-y=17 that give u the same thing. Cross out the - 2x and 2x then subtract 2y by y which will leave u with y and subtract - 20 by 17 that will leave with - 3. So y = - 3

Another way to do it is

2x-y=17

x-y=10, x=10+y

substitute x=10+y for x in 2x-y=17 and get

2 (10+y) - y=17

20+2y-y=17

20+y=17

subtract 20 from both sides

y=-3

subsitute y=-3 into equation x-y=10

x - (-3) = 10

x+3=10

subtract 3 from both sides

x=7

or subsitute into 2x-y=17

2x - (-3) = 17

2x+3=17

subtract 3 from both sides

2x=14

divide both sides by two

x=7