Alvin and Bob had a total of 60 marbles. Alvin gave 1/4 of his marbles to Bob. Bob then gave 1/3 of the total number of marbles he had to Alvin. In the end, each of them had the same number of marbles. How many marbles did Alvin have at first?
By the way, we cannot use algebra to solve this question.
Because this is a primary school(5th Grade) question in Singapore, we can't use algebra to solve since they haven't learnt it.