Question 9325
x-y=3
x+y=7

first you need to get either x or y alone in one of the equations.

x=3+y
now you need to substitute this back into the second equation

(3+y)+y=7

2y+3=7
2y=4
y=2

now that you have the y value you can plug it back in to either equation to get the x value.
x+2=7
x=5