3y-16z
=2(2x+2y-7z)-(4x+y+2z)
=(-3)*2-7
=-13
15y+10z
=4(x+4y+3z)-(4x+y+2z)
=4*8-7
=25
根据3y-16z=-13
15y+10z=25
得,90z=(15y+10z)-5*(3y-16z)=25-5*(-13)=90
所以z=1 y=1x=1