Problems on Numbers - General Questions

A number exceeds its one-fifth by 84. What is the number?

When 4 times a number is increased by 13, the result is 85. What is the number?

The difference between a two-digit number and the number obtained by interchanging its digits is 45. What is the difference between the two digits?

The sum of two numbers is 118 and their difference is 6. What is the larger number?

The sum of two numbers is 28 and their product is 187. What is the sum of their squares?