Answer:
126.
Step-by-step explanation:
This is the number of combinations of 4 cards from 9 cards:
= 9C4
= 9! / 4! 5!.
A quick way of calculating this is
9*8*7*6
----------- = 9*2*7 = 126 combinations.
4*3*2*1
-3 is the answer
Think of the total as 1/5 + 1/5 + 1/5 = 3/5
You have THREE fifths of material.
You use ONE of those fifths.
That leaves you with TWO fifths.
