60 sixth graders 40% of the sixth graders will attend.

D

Step-by-step explanation:

So we want to evaluate the expression:

First, let's figure out the value of f(-9) and g(6).

From the graph, we can see that a point on f(x) is (-9,4). In other words, f(-9)=4.

Also, a point on g(x) is (6,6). This means that g(6)=6.

Substitute:

Multiply:

Add:

So the answer is D.

And we're done!