please, help me to solve 5,6,7 questions...

Writing functions: a. Write a function definition for a function called mean which takes two doubles as parameters and returns their (arithmetic) mean as a double. b. Then write a function call to mean to evaluate the mean of 10 and 100 and output it to the console. Write a full program (including header, namespace, etc.) that reads from the user an integer between 10 and 99 and outputs the following based on the input: The first digit is strictly less than the second digit. The first digit is strictly greater than the second digit. The two digits are equal. Write a full program (including header, namespace, etc.) that takes as console input two strings from the user and exchanges the last character of the first string with the first character of the second string, and outputs the resulting strings to the console