x = 5 - y...so sub 5 - y in for x in the other equation
5(5 - y) - 4y = 7...distribute thru the parenthesis
25 - 5y - 4y = 7...simplify
25 - 9y = 7....subtract 25 from both sides
-9y = 7 - 25
-9y = - 18...divide both sides by -9
y = -18/-9
y = 2
x = 5 - y
x = 5 - 2
x = 3
solution is (3,2)
