解方程 3(2X-Y)+4(X-2Y)=87 2(3X-Y)-3(X-Y)=82 1-0.3(Y-2)=(X+1)/5 (Y-3)/4=(4X+9)/20-15 X+Y=3(2X-Y)+4(X-2Y)=87 2(3X-Y)-3(X-Y)=82 1-0.3(Y-2)=(X+1)/5 (Y-3)/4=(4X+9)/20-15 X+Y= 28000.96X+0.64Y=2800*0.92

3(2X-Y)+4(X-2Y)=87 10x-11y=87 (1)
2(3X-Y)-3(X-Y)=82 3x+y=82 (2)
由(1)+11*(2)得，43x=87+902 ==> x=989/43=23 (3)
将（3）代入（2）中，得 y=82-3*23=13
1-0.3(Y-2)=(X+1)/5 等式两边都乘以10得，10-3y+6=2x+2 即 2x+3y=14 (1)
(Y-3)/4=(4X+9)/20-15 等式两边都乘以20得，5y-15=4x+9-300 即 4x-5y=276 (2)
由2*（1）-（2）得，11y=-248 ==> y=-248/11,代入（1）中得，x=449/11
0.96X+0.64Y=2800*0.92 ==> 0.32x+0.64(x+y)=2800*0.92 又 X+Y= 2800 ==>
0.32x+0.64*2800=2800*0.92 ==> 0.32x=(0.92-0.64)*2800 ===> x=2450
y=2800-x=2800-2450=350

(1)原式：3(2X-Y)+4(X-2Y)=87 2(3X-Y)-3(X-Y)=82=> 10x-11y=873x+y=82 (=> y=82-3x代入10x-11y=87)=> 解为：x=23,y=13(2)原式：1-0.3(Y-2)=(X+1)/5 (Y-3)/4=(4X+9)/20-15 => 2x+3y=144x-5y=-276=> 4x+6y=284x-5y=-27...