12x+20y=20x+15y

解方程组 x+2y=1.5,12(x+y)+15y=20 解方程 {x+y=20 x-y=12 x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 20(x+y)=12(y+z)=15(z+x),且xyz不等于零,求x:y:z= 已知20（x+2y）=15（y+3Z)=12（z+5x),则x:y 有这样一道题,计算：（x-y)[(x+y)(x+y)-xy]-(x-y)[(x-y)(x-y)+xy]的值,其中x=20 化简(x+y)-(2x+y/2)-(3x+y/6)-(4x+y/12)-(5x+y/20)-……-(10x+y/90) 方程组12/x+15/y=20 x=y-0.3怎么解 x/20+y/15=40 y/12+x/6=75,解方程, {x+y=100,20%x+12%y=100×15%,解方程组,