x+y=90 5/8x＋5＝3／5y　　x,y分别是多少?

5X +7y=145 5x+3y=105 X是多少.Y是多少 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) x-5y＝13且3x+y＝20,x.y分别等于多少? 若y:x:z=5:3:8,且7x+3y－5z=8,则x.y.z分别是多少? (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y 3x-2y=9 x-3y=2 x+y=5 x+2y=3 y=x 2x+y=8 已知x.x+y.y-6x-8y+25=0,求3x.x+5y的值 (3x-4y)(5x-4y)-(7x-8y)(6y-5x) （5x+3y)(3y-5x)-(4x-y)(4y+x)= 5(x-y)^2-(x-y)-8(x-y)^2-3(x-y) 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5