The answer is 93
If we sorted out the number of each hours, the sequence will look like this
57 _ 69 _ 81 _ x _ 105
(in which x is the fourth hour of work)
We can see from the sequence that each hours, the mailman add additional 12 letters.
(69 - 57 = 12)
(81 - 69 = 12) . . . . proof
So, the amount of letters on the fourth hour would be:
81 letters + 12 letters = 93 Letters
I believe it would be the first choice
Hope that helps!
easy 214.7 because if it was rounded it would be 214.700 an this is way bigger than 214.275
15h + 80 = 140
If you wanted to solve how many hours he worked:
15h + 80 = 140
15h = 60
h = 4.