How do you find the percentage of a number?

Jack has a piece of red ribbon that is two times as long as his piece of blue ribbon. he says that he can use two different equation to find out how long his piece of red ribbon is compared to his piece of blue ribbon is. is he correct? explain his reasoning

Is the power produced directly proportional to the wind speed, give reasons for your answer?

If g^-1(x) is the inverse of g (x) which statement must be true