If Tomorrow is Monday, what will be the day after 90 days

How do we solve it ?

If tomorrow is monday, today is sunday.

A week has 7 days " Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday ".

90 / 7 = 12 ( Remainder = 6)

So you can say that after multiples of 7 days, the day will repeat itself as sunday.

Hence after 84 days sunday will occur again.

So we calculate after the remainder (6) , the answer is Saturday.

Simple Logic = And whatever the remainder obtained is, add that to the day.