What is being done to the variable in the equation a/-7 = 84?

I'm being volume of cylinder with 13 in. radius and 30 in height answer choices in pic

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

Select the margin of error that corresponds to the sample mean that corresponds to each population: a population mean of 25, a standard deviation of 2.5, and margin of error of 5%