Problems on Numbers - General Questions

When 4 times a number is increased by 19, the result is 119. What is the number?

The sum of two numbers is 25 and their product is 100. What is the sum of their squares?

The difference between a two-digit number and the number obtained by interchanging its digits is 9. What is the difference between the two digits?

Two numbers are such that 4/7 of the first equals the second. If the first is 28, what is the sum of the numbers?

The sum of three consecutive integers is 24. What is the largest of them?