If Today Is Tuesday, what was the day before 30 days

How do we solve it ?

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

30 / 7 = 4 ( Remainder = 2)

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

Hence before 28 days Tuesday would occur again.

So we calculate before the remainder (2) , the answer is Sunday.

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