What is the answer to the problem above fast

Is experimental probibilty the same as the observed frequency in math? i need the answer asap!

One cell phone plan charges $20 per month plus $0.15 per minute used. a second cell phone plan charges $35 per month plus $0.10 per minute used. write and solve an equation to find the number of minutes you must talk to have the same cost for both calling plans.

Explain how you can show five less than a number using algebraic expression