(7y-3z)-(8y-5z)得多少,
问题描述：
(7y-3z)-(8y-5z)得多少,
答
(7y-3z)-(8y-5z)
=2z-y过程(7y-3z)-(8y-5z)=7y-3z-8y+5z=7y-8y-3z+5z=(7-8)y+(-3+5)z=-y+2z=2z-y