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Option 3 : 28 years

Given∶

Tony’s age was 30 years older than his sister Sara.

Mother Marry was 20 years older than this brother Sam.

Sara is 4 years elder than Sam.

After 2 years, the average age of Tom’s family is 20.

Formula Used∶

Concept of Average, Linear Equations.

Calculation∶

Let the present age of Sam be ‘x’ years

Then, Sara’s age = (x + 4) years

Tony’s age = 30 + x + 4 = (x + 34) years

Marry’s age = (20 + x) years

So, the sum of their ages = x + x + 4 + x + 34 + 20 + x = 4x + 58

After 2 years, the sum of their ages will increased by 2 × 5 = 10 years

∴ The sum of their ages after 2 years = 4x + 58 + 10 = (4x + 68) years    ----(1)

Also, The average age of 5 members of Tom’s family = 20

So, Sum of their ages = 20 × 5 = 100 (2)

On equating eq. (1) and (2), we get

4x + 68 = 100

⇒ 4x = 32

⇒ x = 8

Marry’s age = 20 + x = 20 + 8 = 28 years.

∴ When Tom was born, Marry’s age was of 28 years.

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