Since the balls and the boxes are not distinguishable, we only care about how many balls are in each box, not which balls or which box. Let x be the number of balls in one box and y be the number of balls in the other box. Then we have x + y = 5 and x, y are non-negative integers. We can solve this equation by using the stars and bars method, which says that the number of solutions is equal to the number of ways to arrange 5 stars (representing the balls) and 1 bar (representing the division between the boxes) in a line. For example, one possible arrangement is *|****, which means x = 1 and y = 4. The number of ways to arrange 6 symbols in a line is 6!, but we have to divide by 5! to account for the fact that the stars are not distinguishable, and by 2 to account for the fact that the boxes are not distinguishable. Therefore, the number of ways to put 5 balls in 2 boxes is 6! / (5! * 2) = 3. 
How many ways are there to put 5 balls in 2 boxes if the balls are not distinguishable and neither are the boxes?