There are 3 methods to solve this. elimination substitution and graphing but i am going to use the elimination method.
x+2y=17
x-y =2
0+3y =15 ( subtracted down to eliminate the x)( x-x=0, 2y-(-y)=3y, and 17-2=15)
3y=15 (divide both sides by 3 to solve for y)
y=5
substitute the y=5 in any of the above equations and solve for x
ie... ( meaning where you find y in the equation, u replace it with a 5)
it will be easier to solve for x in (x-y=2) so i will use that one.
x-(5)=2 ( add 5 on both sides to solve for x)
x=7