Random Puzzles 

Workings

Hint
Something's wrong with the letter O, and the word 'oifoeront' is important to the answer.

Answer
15 different letters: acdefhilmrstvwy.

Reasoning
The sentences should read:

As you can see, my printer replaces every third letter with the letter 'o'.

How many different letters have been replaced?

Workings

Hint
The chemical symbol for iron is Fe.

Answer
Yttrium.

The element's symbols are spelling February:

   iron (Fe) + bromine (Br) + uranium (U) + argon (Ar) + yttrium (Y)

Workings

Hint
Vowels (AEIOU) and consonants are each worth a different number of miles.

Answer
2,200 miles.

Vowels (AEIOU) are worth 300 miles and consonants are worth 200 miles.

Double-Checking
Argentina has 4 vowels (AEIA = 4 x 300), and 5 consonants (RGNTN = 5 x 200), for a total of 1,200 + 1,000 = 1,200 miles.

Workings

Hint
Think of squares and cubes.

Answer
512.

Each term alternates between a square and a cube, 8 3 = 512.