What is f(g( a mapping diagram is shown

We want to know f( g (13) ), here g(13) is just a number, so you are evaluating f in a number, first we need to know the value of g(13). Looking in the diagram you can see that g(13) = 16.

So f(g(13)) = f(16)

Also, looking in the diagram you can see that f(16) = 32

So, f ( g (32) ) = 32

b). 4320 have a nice day