x-y=2
xy=15
x=2+y
(2+y)y=15
2y+y²=15
y²+2y-15=0
y²+5y-3y-15=0
y(y+5)-3(y+5)=0
(y-3)(y+5)=0
y=3 ∨ y=-5
x=2+3 ∨ x=2+(-5)x=5 ∨ x=-3
(5,3) ∨ (-3,-5)
