SOLUTION
Notice that there are 5 total topings
Since Helen is to select three topings then order does not matter
Hence the total number ways can be determined using combination rule:
That is:
This gives:
Therefore there are 10 ways Helen can combine the topings:
The topings are
pepperoni(P), sausage(S), ham(H),
mushroom(M), and onions(O)
The chart is shown: