only looking for the answers to 18 and 24 using visual studio C+

18. Find the sum 1+4+7+10+13 + ... +100 19. Find the sum 2.1 +4.1 +6.1 + ... +200.1 20. Find the factorial 21! 21. Given real numbers in an array of observations, find the mean value 22. Given real numbers in an array of observations, find the standard deviation of the numbers 23. Given real numbers in an array of observations, find the maximum value 24. Find the value of 1 + + + ... +