Question

After 15 yesrs , marys age will be four time of her present age . find her age

Answer 1

Let Mary's present age be x years.

After 15 years.i.e.x+15, her age will be 4 times her present age.

x+15=4x.
15=4x-x.
15=3x.
15/3=x.
5=x.

Mary's present age is 5 and after 15 years she will be 5+15 years=20 years.

Answer 2

Let the Present age of Mary be x years
After 15 years ,age of Mary = x+15
According to the question
4x =x+15
4x-x=15
3x =15
x=5