1/3 + 2/5 = 5/15 + 6/15 = 11/15ths of the guests drank soda or orange juice. That left 1 - 11/15 = 15/15 - 11/15 = 4/15 who had nothing to drink. Let x represent the number of guests:Multiply both sides by the reciprocal 15/4: There were 60 guests. Edwin