Question

Mary is 3 times as old as her son. In 12 years Mary will ve twice as old as her son. How old are each of them now

Answer 1

Mary is 36 years old

Her son is 12 years old

Explanation:

Let's assume, that Mary's son is x years old and Mary is 3x years old

Let's write 2 equations according to the given information:

x = 3x (Mary is 3 times older than her son)

3x + 12 = 2(x + 12) (after 12 years, she will be 2 times older than her son)

3x + 12 = 2x + 24

3x - 2x = 24 - 12

x = 12

That means, Mary's son is 12 years old

Mary is 3 × 12 = 36 years old

Answer 2

Let's assume the age of Mary's son as "x".

According to the given information, Mary is 3 times as old as her son. So, Mary's age will be 3x.

Also, given that in 12 years Mary will be twice as old as her son.

So, after 12 years, Mary's age will be (3x + 12) and her son's age will be (x + 12).

According to the given information,

3x + 12 = 2(x + 12)

3x + 12 = 2x + 24

3x - 2x = 24 - 12

x = 12

Therefore, Mary's son is 12 years old now.

And, Mary's age is 3x = 3(12) = 36 years.

Hence, Mary is 36 years old and her son is 12 years old.