Question

Yvette younger brother just turned 3 years old. Fred brother is now 30 months old who's brother is older

Answer 1

3 years is 12 months x 3  which is 36 months
Therefore Yvette bother is older because he is 36 months which is 3 years 

Answer 2

You can convert 3 years into months
there are 12 months in one year
so 3 years would be (3*12) months
which would be 36 months

then compare 36 months to 30 months
which is bigger?

36 months
therefore Yvette's younger brother is older.