2m-3n=1 ...(1)3m+5n=12.9 ...(2)(1)*5+(2)*3：10m+9m=5+38.719m=43.7m=43.7/19=2.3(2)*2-(1)*(3)10n+9n=25.8-319n=22.8n=22.8/19=1.2x+1=5(y-2）...(1)3(2x-5)-4(3y+4)=5 ...(2)整理:x-5y=-11 ...(3)6x-12y=36,即x-...