This question is confusing. Please help me!

What value of x is in the solution set of –5x – 15 > 10 + 20x?

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.

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).