Answer:
60
Step-by-step explanation:
Use r-combinations.
Treat it as though u are filling in 6 slots
_ _ _ _ _ _
1. First fill in the 7s, there are three of them and 6 ways to do so
so (6 Choose 3)
2. then fill in the 2s, now with the 3 slots taken up by the 7, 3 slots left.
So its (3 Choose 2).
3. and only 1 way to fill in the 8. (1 choose 1)
By multiplicative rule,
(6C3) * (3C2) * (1C1) = 60
