The average age of two brothers is 9 years. If the average age is increased by 9 years when their mother's age is also included, then the age of the mother is:

The average age of 4 sisters is 7 years. If we add the age of mother, then the average increases by 6 years. Find the age of the mother.

The average age of 30 boys in a class is 15 years. If we include the age of two teachers the average age increases by 1. Find the sum of ages of the two teachers.

The average of four numbers is 12.5. If each number is increased by 2.5, then the new average will be:

Five years ago, the average age of X₁, X₂, X₃ and X₄ was 50 years. If we include X₅, the present average age of all five is 56 years. Then the present age of X₅ is

The average of 6 numbers is 5. The first number is increased by 2, second by 4, third by 8 and so on. The average of new numbers is