The conversion from fahrenheit to celsius is more complicated. The formula for this transformation is: Fahrenheit = Celsius * 9 / 5 + 32 . It looks complicated and you may thing that you will never be able to do it without a calculator, but you can, let me explain you the easy way. You have the temperature in Celsius, double it and then add 32. It is not exact, but 9/5 is 1.8 which is close to 2. For exact conversion, after you double the celsius value you can substract 10 percent from the value, which is not very complicated. For example, take 28 degrees, double it you get 56, 10% from 56 is 5.6, very simple , you have 50.4, and then add 32 which will make it 82.4.
If you want a quick conversion and you are in front of a computer with internet conectior or you are using a mobile device, use an online temperature converter: Celsius to fahrenheit
The rankin scale is very simple to convert to, get your fahrenheit temperature and add 459.6 .