Help, got a task i don't know how

Question

1. Write a program that calculates the largest number from the series of integers: a, b, c, 2. For a given numeric prefix <a, h> (closed interval) where a <b, find an integer x belonging to the interval h <a, b > I satisfying the relationship x (a + b) / 6. If such a number does not exist, the program is to display -1. 3. Write down the second integer from the interval <a, b> divisible by 4. 4. For a duality integer x that belongs to the interval «0, 1000> one can find the second number 1000 x belonging to the interval <0, 1000> Write a program that checks if for any integer xi of the interval <a, b> there exists a number y = hx that also belongs to the interval <a, b>. 5. Write a prugram that calculates the number of numbers that are divisible by 11 among 21 integers less than the integer a.

Answer 1

Google "modulo operator c++"