Those have difficulty in working out the maths problems can ask the maths teathers for advice.
问题描述：
Those have difficulty in working out the maths problems can ask the maths teathers for advice.
这是一道改错题,请问哪里错了?为什么错了呢?
答
Thosewho have difficulty in working out the maths problems can ask the maths teathers for advice
如果不加who
就出现一个主语两个谓语的错误了