Ana has 4 coins with different values(5, 10, 20, 50) and you are asked to find how many different sums they can make. You can see every value as a separate combination and multiply it.
There is 1 coin for every value and it can be either used or not used, so there are two probabilities for each coin value. The calculation would be:
C(2,1)= 2!/1!= 2
There are 4 values of coins, so the total probability would be:
4 * C(2,1)= 4*2=8 ways