I wrote it out this time, so I didn't forget any work like last time. LOL
The curves

and

intersect at approximately

. The area is then
11x11 is 121 , if that is what ur asking
We know that Billy caught total 4+10=14 fishes including trout and catfish.
P(catching the catfish):
10/14
Simplify that into 5/7. As a result, the probability that the next fish that Billy catches will be a catfish is 5/7. Hope it help!