Suppose you earn $6 per hour at your part time job what will your new rate be after a 2.5% raise

2.5% means 0.025 .
After an increase of 2.5%, the new rate is (1.025) x (the old rate).

1.025 x $6.00  =  $6.15 per hour.

If you work a full 40 hours in some week, you will be blessed with
a full $6 more for the week of toil than you would have collected
at the old rate.

You were not overpaid before the raise, and you must not allow
your boss to act as if you should kiss his ring or prostrate yourself
before him in return for 2.5% .  It was not too long ago that 2.5% was
tantamount to being shown the way to the door, and a tacit suggestion
that you consider following in the way of the arrow.