Difference between 问 and 让 "to ask"
问 = ask (to answer question) e.g. 问他今年多大 - Ask him how old he is (It is a question I want to know the answer)

让 = ask (to do something; request; demand) e.g. 我去让他來道歉 - I'll go ask him to apologize (ask here is actually a request or demand) - 让 (ask) here is the same as (make)


Just remember 问 = ask a question; 让 = ask someone to do something.