5x - 4y = 7

x = 5 - y

Substituting value of x in first equation

5 (5-y) - 4y = 7

25 - 5y - 4y = 7

25 - 9y = 7

25 - 7 = 9y

18 = 9y

18/9 = y

y = 2

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)