3x+4y=403 (1)
4x+3y=416 (2)
(1)式两边同时乘4得:12x+16y=1612 (3)
(2)式两边同时乘3得:12x+9y=1248 (4)
(3)式减(4)得:7y=364
y=52
y=52代入(1)式得:x=65