Question

The sum of the present age of a mother and her son is 35 and the difference is 25 years.find their present age.(By substitution or elimination method).​

Answer 1

Son = 5 years old

Mum = 30 years old

Explanation:

Let the Mum be M and the Son be S;

`M + S = 35` --- Sum

`M - S = 25` -- Difference

Required

Find M and S (their ages)

Using elimination method; Add both equations to eliminate S

`M + S = 35`

`M - S = 25`

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

`M + M + S - S = 35 + 25`

`2M = 60`

Solve for M

`M = (1)/(2) * 60`

`M = 30`

Substitute 30 for M in
`M + S = 35`

`30 + S= 35`

Solve for M

`S = 35 - 30`

`S = 5`

Hence:

Son = 5 years old

Mum = 30 years old