How many ways can you find to make the number 10, by adding or subtracting prime numbers? The same numbers but in a different order count as the same answer. (Prime numbers are only divisible by themselves and 1 so they are 2, 3, 5, 7, 11, 13, ...)
Answer is like
2+3+5, 2+2+3+3, 3+7, 5+5, 13-3, 17-7, 23-13, 29-19, 41-31, 47-37, 53-43, 71-61 and so on.....