This is blatantly a homework question so I'll just give a few hints...
First find the no. of routes to (5,7) and (4,3) and then subtract the latter from the former got it?
So, to get to (5,7) Marvin must take 5 steps right and 7 up in any order.
Similarly to get to (4,3) he does 4 right and 3 up in any order.
Now, no. of routes to (5,7)\(={12!\over 5!7!}\)
Similarly you can find the no. of routes to (4,3).
There you go, I've given enough hints for this one..😏