7x + 3y = 15
2x = y+8
2nd equation can be rewritten as x = y/2 +4
replace x in 1st equation with that:
7(y/2+4) +3y = 15
distribute:
7y/2 + 28 +3y = 15
multiply 3y by 2/2 = 6y/2
7y/2 + 6y/2 + 28 = 15
13y/2 + 28 = 15
13y/2 = -13
13y = -26
y = -26 / 13 = -2
2x = -2 +8
2x = 6
x = 6/2 = 3
x=3, y = -2
solution is (3,-2)
