[pdurrant]

Originally Posted by red_pheonix

That is a great explanation pdurrant but it still doesn't make any sense to me.

The task is to make sums that add up to each number (1,2,3,...) in turn.

If we were unlimited in the numbers we could use, this would be trivial.

So we are limited to using exactly four specific numbers (1,3,5,7) in our sums.

1*(3+5-7) = 1
1+3+5-7 = 2

etc.