I don't think this question is complete but here's ur answer
One pizza serves four people so, you will need 10 pizzas for 40 people so that make the answer (A.)
This is how the graph should look like
<span>A=1/2(a+b)h for h.
First, you need to get rid of 1/2, so divide both sides by 1/2.
A/(1/2) = (a + b)h
You can simplify the </span>A/(1/2) by multiplying by the reciprocal of 1/2, so 2/1.
2A = (a + b)h
Now divide both sides by (a+b).
2A/(a+b) = h