This is the solution to Crease puzzle #11. The puzzle gives you a strip of 8 numbers and asks you to fold it 2 times to reach a strip of 3 numbers.
Folding only adds numbers together, so the total never changes. Both strips add up to 33. Your largest target number, 13, must be a stack of several cells added together.
The strip has 8 cells and the target has 3, so the folds together must remove 5 cells. A fold removes as many cells as its shorter side has.
The first fold goes between cell 4 and cell 5, counting cells from the left.