hello, this is math and I need help ❤️ pls and ty ONLY SERIOUS ANSWERS

The bicycle with a 30-inches diameter rolls approximately 28.8 more than a tire with the diameter with 21-inches.
How to solve:
C = 3.14 x 30 ⇒ 94.2477796077
C = 3.14 x 21 ⇒ 65.9734457254