Can someone teach me how to do this type of thing?

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

Bobby bought 1.12 pounds of turkey at a cost of 2.50 per pound. carla bought 1.4 pounds of turkey at a cost of 2.20 per pound. who spent more and by much?

From the beginning of the day the temperature rose 15 degrees so that by 4 pm it was 87 degrees. what was the temperature at the start of the day