Does anyone know how to do this i have no clue! is needed pls

What is the value of the expression 9+n/3-6 when n = 12? 1. 5. 7. 12.

Using pert, adam munson was able to determine that the expected project completion time for the construction of a pleasure yacht is 21 months, and the project variance is 4. a) what is the probability that the project will be completed in 17 months? b) what is the probability that the project will be completed in 20 months? c) what is the probability that the project will be completed in 23 months? d) what is the probability that the project will be completed in 25 months? e) what is the due date that yields a 95% chance of completion?

If the tip varies directly with the number of guest which equation represents between the tip, t, and the number of guest, g?