kkk579
hello
i’ve heard du just takes a lot of his problems out of textbooks?? the main ones i’ve heard is signpost, cambridge and terry lee (if i’m not mistaken).du is popular amongst ruse students in particular, and their trials and exams are known to be quite wild, so du's materials which focus on harder wilder problems are meant to help them get accustomed to seeing these kinds of questions and thus ace those exams (at least that's what i think)
and never underestimate how much the parents of a selective kid are willing to pay for their child's tutoring tbh. they'll do whatever it takes as long as their kid ends up getting the good marks