解方程组：4x-9n=17.(1)；3x十y十5n=18.(2)；x十2y十3n=2.(3)；2×(2)-(3)得 5x+7n=34.(4)；(4)-(1)得x+16n=17,故x=17-16n.(5)将(5)代入(1)式得4(17-16n)-9n=68-73n=17,73n=51,故n=51/73；将n=51/73代入(5)式得x=17-...