x-y=20,(1-30%)x+(1+20%)y=226解的过程

Question

x-y=20,(1-30%)x+(1+20%)y=226解的过程

Answer 1

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Answer 2

x-y=20 .............................(1)

(1-30%)x+(1+20%)y=226
0.7x+1.2y=226
7x+12y=2260 ......................(2)

(1)×12+(2)得 19x=2500
x=2500/19
代入（1）得 2500/19-y=20
y=2120/19

方程组　的解为 x=2500/19,y=2120/19

Answer 3

　　由x - y = 20;
　　得x = 20 + y;

　　又（1 - 30%）x + (1 + 20%)y = 226;
　　带入x = 20 + y;
　　得 0.7 (20 + y) + 1.2y = 226;
　　即1.9y + 14 = 226;
　　得y = 111

　　又 x = 20 + y
　　即x = 20 + 111 + 131;