Question

When i was two, my brother was half my age
now i am 100. what is my brothers age

Answer 1

99 as 2 halved is 1 so 100-1= 99

Answer 2

When you were 2, your brother were 2/2=1. So you are one year older than your brother.
If you are 100 now, then your brother is 100-1=99.