SOLUTION: a mother is 15 years older than her daughter. The sum of the age of the daughter and the mother is 40. Wha is the age of the mother?

Hi

Let x represent daughter's age 

15 years older does not work, using 18 years older for the mother as an example

 Mother  + Daughter = 40

 ( x + 18) + x = 40

       2x = 22

        x = 11, the daughter's age, mother is 29