$1.$ Write a program that converts Fahrenheit temperatures to Celsius temperatures. The program should ask the user to enter a temperature in Fahrenheit and then display the temperature converted in Celsius $($Lastname$\_$Lab$2-1-1.$py$).$

The formula is as follows:

Example for the output:

$75$ F $=24$ C

$2.$ Calculate the sum of digits of the three$-$digit number. The program should ask the user to enter any three$-$digits number and then display the sum of all digits. In the process of computing operations, you should use only arithmetic operators $//$ and $\%($Lastname$\_$Lab$2-1-2.$py$).$

Example for the output:

The sum of digits of number $123=6$

$3.$ Calculate the sum of digits of the four$-$digits number.