x+y=18 30%x+75%y=18*50%

xy+x-y=18,x,y各等于几 5x+7y=7x+5y+18 解方程组{x(x+y+z)=6,y(x+y+z)=12,z(x+y+z)=18 解方程组:2/(x+y)+5/(x-y)=18 9/(x+y)-10/(y-x)=66 解方程组：2/(x+y)+5/(x-y)=18 9/(x+y)-10/(y-x)=66 解方程组24/(x+y) +24/(x-y) = 7/3 ,8/(x+y) +18/(x-y) = 4/3 已知y=根号(x-8)+根号(8-x)+18,求代数式[(x+y)/(根号x+根号y)]-2xy/(x根号y-y根号x) 2x+y=15 x+2y=18 x=?y=? 请帮我解方程第三道x+y=18{30%x+75%y=18*50% 方程组：x+y=18 30%x+75%y=18乘50%.怎么解?帮帮忙,先谢谢你们了! y/3-x+1/6=3 2(x-y/2)=3(x+y/18) 已知y=√(x-8)+√(8-x)+18,求代数式 (x+y)/(√x-√y)-2xy/(x√x-y√x) 的值