4 trays are needed because your number is 3.75 and you need another tray for the rest
We want to find the value that makes

To find it we must look at the standard normal table, using the complementary cumulative table we find that

Then, using the z-score we can find the minimum score needed, remember that

Where
σ = standard deviation
μ = mean
And in our example, x = minimum score needed, therefore

Rounding to the nearest integer the minimum score needed is 568, if you get 568 you are at the top 20.1%.
Answer:
Answers in explanations, hope they're correct!
Step-by-step explanation:
12. You will be using 0 gallons of gas when traveling 0 miles.
13. 20 gallons
14. (2,6)
15. You will package 15 dozens of cupcakes after 5 hours