某学生把7乘(m-3)抄错为7m-3,若正确答案为x,抄错的答案为y,则x-y等于多少?

问题描述:

某学生把7乘(m-3)抄错为7m-3,若正确答案为x,抄错的答案为y,则x-y等于多少?

x-y
=7*(m-3) - (7m-3)
=7m-21 -7m+3
=-18