Valerie is ordering salad and drinks for her friends. salad cost $7 each, drinks cost $3 each and there is a $5 delivery charge per order. she has $50. if she buys 3 salads, what is the maximum number of drink she buy?

7*3=21 So, 21 dollars is needed for the salads.
Add on 5 dollars for the delivery charge. We are now at 26 dollars. 
50-26=24... So, we have 24 dollars left to buy drinks. That means we can buy 8 drinks. (Just divide 24 by 3 to get 8)

The answer is 8 drinks.

Salads are $7 each. If Valerie buys 3 salads, 3*7 = 21, that is $21. There is also the delivery charge of $5 for a total of $26. Valerie has $50 but already spends $26 on the salads and for delivery. Subtract 26 from 50, 50-26 = 24, so Valerie still has $24 to spend on drinks alone. If each drink is $3, we divide 24 by 3 to get 8. Valerie can buy 8 drinks.

Do you need with the x value for the minimum? its always between the two intercepts for a parabola