Brain Teasers and Puzzles 

Workings

Hint
There are quite a few anagrams, one of which is LEAST.

Answer
Least, slate, stale, steal, tales, teals.

Remember that the question asked for common words.

Workings

Hint
The answer is in the question.

Answer
Edam.

MADE backwards!

Workings

Hint
The list is related to numbers.

Answer
Llama.

The length of each word is the same length as the numbers one, two, three, four, five, six, etc.

The next number is SEVEN, which has 5 letters, and llama is the only word with 5 letters.

Workings

Hint
The answer is in the words given.

Answer
Slow.

Reasoning
Take the third letter of the first word
   + the second letter of the second word
      + plus the first letter of the first word
         + plus the fourth letter of the second word.

Double-Checking
3-1- [1234] -2-4
s-f- [fast] -a-t
o-s- [slow] -l-w