17.It took our teacher and we three hours to work out this difficult maths problem.

we --us
跟our teacher 并列 在took后应用宾格

WE改成OUR
WE是主格,OUR是宾格

It took our teacher and us three hours to work out this difficult maths problem.
take跟宾格
没有it take she/he sometime to do
是it take her/him

we 改成 us
It takes sb. to do sth.
在这里是有our teacher(s)和us一起做所以都应该是宾格

took 在本句中作为谓语动词。谓语后面应该是宾语，同时 宾语应用代词的宾格。we 应该为 us

take so 多长时间 to do sth. 中间不能加主格WE,应该是宾格US就没问题

it took our teacher and us three hours to work out this difficult maths problem.