Question

The ages of John and David are in the ratio 5:7. Four year later, the sum of their ages will be 56 years. What are their present ages?

Answer 1

Let John's age = 5 x and David's age = 7 x .

A/Q, 5 x + 7 x + 8 = 56

⇒ 12 x = 48

∴ x = 4

John = 20 years

David = 28   ''  ''

Answer 2

Here is your answer

$\rule{120}{2}$

Let the age of John be 5x and age of David be 7x

After 4 years, their ages will be 5x + 4 and 7x + 4

The sum of their ages = 56

According to the question,

5x + 4 + 7x + 4 = 56

12x + 8 = 56

12x = 56 - 8

12x = 48

x = $\frac{48}{12}$

x = 4

∴ Age of John = 5x = 5 * 4 = 20 years

∴ Age of David = 7x = 7 * 4 = 28 years