Factoring by grouping review, does anyone know how to do this or at least give me an explanation?

Which function is represented by the graph

Giuseppi's pizza had orders for $931.00 of pizzas. the prices were $21 for a large pizza, 514 for a medium pizza, and $7 for a small pizza. the number of large pizzas was two less than four times the number of medium pizzas. thenumber of small pizzas was three more than three times the number of medium pizzas. how many of each size of pizza were ordered?

F(x)=x/2-2 and g(x)=2x^2+x-3 find (f+g)(x)