#15 E. Z. Lockett forgot her 3 number combination to the patlock shown. SHe knows that all of the numbers have a 3 as one of its digits and all 3 numbers of the combo are differen. How many combos can she try? the lock is circular and the numbers range from 0 to 39
#42 [unparseable or potentially dangerous latex formula] what does X equal?
#50 [unparseable or potentially dangerous latex formula], where k and n are relatively prime, then n+k=?