Question

A father and his son decide to sum their age. The sum is equal to sixty years. Six years ago, the age of the father was five times the age of the son. Six years from now the son’s age will be?

Answer 1

20.

Explanation:

x = father's age and y = son's age,

x + y = 60

x - 6 = 5(y - 6)

x - 5y = -24

Subtract this from first equation:

6y = 84

y = 14

So the son's age is 14.

Six years time son will be 20.

Answer 2

20

Explanation:

To solve this you have to make a system of equations.

Since the father and son's age sum up to 60, the first equation will be:

f + s = 60

Secondly, since the father's age is 5 times the age of the son 6 years ago the equation will be:

6 - (5s) = f

Now, you have to solve the first equation to let it equal to s

f + s = 60

f = 60 - s

Plug in

6 - 5s = 60 - s

+s +s

6 - 4s = 60

-6 -6

---------------------

-4s = 54

----- -----

-4 -4

s ≅ 14

14 + 6 = 20