Choose without if or Case

Question

Hey guys im new in the Programming, i have a problem with my code . I have to combine 3 calculations celsius to fahrenheit, euro to dollar and metres to feet. I need to choose one of them in the menue like in the code but the Problem is im not allowed to use if case or other things only calculations. Could you help me?
https://code.sololearn.com/ck7Tg0kuGkqB/?ref=app

Answer 1

I tried to solve the problem, this is my result:
https://code.sololearn.com/cs2Ecip0ZISx/?ref=app