If 31st day of a month is Friday, what was the day on 3rd day of that month ?

Thrusday Friday Saturday Sunday

Friday

If the 31st of a month is Friday, that means the 24th (31st - 7), 17th (24th - 7), 10th (17th - 7), and 3rd (10th - 7) will be having the same day. Thus, the 3rd of that month will be "Friday".