How do I find the missing side?

Evaluate the expression for the given value of the variable 2×(c2-5) for c=4

10 ! a train starts from grand city and travels toward belleville 388 miles away. at the same time, a train starts from belleville and runs at the rate of 47 miles per hour toward grand city. they pass each other 4 hours later. find the rate of the train from grand city.

Find the solution of each of the following.