求3x+5y=15 5x+7y=20

已知:3x-5y=0,求x/y,x-y/y,x-y/x 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? |x|=3 |y|=5 |x-y|=|x|+|y| 求 X+Y和 X-Y 等于多少 求x:y:z x:y=7/5:7/3,y:x=7:8 已知7Y=X-3,8Y=X+5 求X和Y 3(x-5)-8y=-x-(-0.5y)=7,求x,y的值 已知2x-y=-3,求代数式5(x-3y)-2(x-7y) x/y=7/5,求3x+y/X-y的值 x+y-z=3 y+z-x=5 z+x-y=7 求x,y,z 求3x+5y=15 5x+7y=20 已知7x+5y/2y-x=3/2,且x≠0,求X/x-4y 5X+Y=3 X+5Y=2 求x和y.5X+Y=3X+5Y=2求x和y. 1、(-y^3)^5/y^3/ y^2+2(-y)^102、(x-y)^7/(y-x)^6+(x+y)^3/(x+y)^23、已知X^a=5,x^b=3,求X^(3a-2b)的值 （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知：4x = 5y,求(x+y) ：y ①7x-3y=1,②-5x+6y,方程组①7x-3y=1,②-5x+6y求x,y