2X+3Y等于7和5X-Y等于9

5x减3 y等于2和2x减3y等于负10 x比y等于3比4,30+x比50+y等于5比7,求x和y 2X+8Y=17,3X+5Y=7,X和Y,等于几? x-y/3=x+y/2 2x-5y=7等于多少 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 x/4+2等于x,x=多少.y/5等于y-3,Y=多少 |x|=3 |y|=5 |x-y|=|x|+|y| 求 X+Y和 X-Y 等于多少 先化简,后求值（x+5y)(x+4y)-(x-y)(x+y),其中,x等于负2又3分之2,y等于7分之3 2x+y大于等于12,2x+9y小于等于36,2x+3y大于等于24,x大于等于0,y大于等于0 (3x-5y)-(3x-2y)等于几 9分之5x+4y等于5分之3x+2y等于2分之x-y 2x等于5y,2z等于3y求3x等于几z