(1)2分之1x-4y=30 ①y-2x=15 ②由②得,y=15+2x ③把③带入①得1x/2-4(15+2x)=302/1x-60-8x=302/1x-8x=30+60-2/15x=90x=-12把x=-12带入③得y=15+2*(-12)y=-9∴方程组的解为{x=-12{y=-9(2)5x+6y=16 ①2x-3y=1 ②由②得...