Question

When i was 10 years old,my brother was half my age.now i am 30 years. How old is he?

Answer 1

Let my age be x
And my brother's age be y
Thus

According to question
when i was 10 years old i.e.,
y = 1/2 (x-10)
y = 1/2x - 5             Eqn 1

and Also
x = 30                       Eqn 2
Putting x from Eqn 2 in Eqn 1

y = 1/2 (30 - 10)
  y = 1/2 * 20
y = 10 Years

Thus his age is 10 years