Subtract the first equation from twice the second. 2(4x +5y) -(8x -3y) = 2(-9) -(21) 8x +10y -8x +3y = -18 -21 13y = -39 y = -3 Then we can find x by substitution into the first equation. 8x -3(-3) = 21 8x = 12 . . . . . . . subtract 9 x = 12/8 = 3/2
