x+y=420 8x+5y=2640

x+y=420 / *(-8) 8x+5y=2640 -8x - 8y = - 3360 8x + 5y = 2640 -3y = -720 / : (-3) y = 240 --------------------------------------- y = 240 x+y = 420 y= 240 x = 420 - 240 y = 240 x = 180

x+y= 420 |*(-5) 8x+5y= 2640 -5x-5y= -2100 8x+5y= 2640 3x= 540 |:3 x=180 180+y= 420 y= 240