Find the number of paths from A to B that pass through point C. (Each step can only go up or to the right.)
There would be 40 paths.
From B to C would be 4C1 or 4C3 which would give you 4. (whichever combination you choose will give you the same answer)
From A to C would be 5C2 or 5C3 which would give you 10.
Now multiply the outcomes:
4*10=40