(7y-3z)-(8y-5z)得多少,

(7y-3z)-(8y-5z)得多少, 2x+5y+4z=0,3x+y-7z=0,则z+y-z得值等于多少? -(7y-3z)-(8y-5z)计算! （7y-3z)-(8y-5z)=?化简! (7Y-3Z)-(8Y-5Z)化简 {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 (7y-3z)-(8y-5z)=-y+2z(7y-3z)-(8y-5z)=7y-3z-8y+5z=(7y-8y)-(3z+5z)=-y-8z为什么是+2z?我觉得没变错, x/(y+z)=1/8,z/(x+y)=1/5解得x/z=2/3 若y:x:z等于5:3:8,且7x+3y-5z等于8,则x,y,z各等于多少? 11x+11z+8y=44,11x+8z+11y=41,11x+7z+12y=40解得多少 若x∶y∶z=3∶8∶7则(x+y+z)∶z为多少 2x+4Y+8Z=100 x,y,z 各得多少 x+Y+Z=1 X+3Y+7Z=-1 X+5Y+8Z=2x+Y+Z=1X+3Y+7Z=-1X+5Y+8Z=2 x+y-z=3 y+z-x=5 z+x-y=7 求x,y,z 2x+3y-z=11 2x+y-5z=8 -2+7y+z=19 {x+y+z=1 {x+3y+7z=-1 {x+5y+8z=2 4x+9y=12 3y-2y+5z=11 5x-6y+7z=13 求：x y z等于多少 已知:x+y+z=0,5x-3y-z=0,求:5x-y+z/2x+8y+7z 的值