How long___it___you to work out such a difficult problem?

How long___it___you to work out such a difficult problem? How long () it () you to work out such a difficult problem?A How long ___ it ___ you to work out such a difficult problem He found () difficult to work out the problem in such a shor It's ______for us to work out such a difficult problem in fi you are clever.you work out the difficult problem in such a Jack is_that knows how to work out the problem.A I think .difficult to work out the problem.A,it B.this C.tha This maths problem is a bit difficult fot me to work out. I find the problem difficult to work out. He is busy to work out the difficult problem. 改错 The problem is difficult for me to work out.