Random Puzzles 

Workings

Hint
A little bit of algebra might help.

Answer
64 pounds.

The head weighs 24 pounds, the body weighs 32 pounds, and the tail weighs 8 pounds.

Reasoning
The trout is made up of the head, body and tail, H, B and T.

We are told that:

    T = 8

(1) H = T + B ÷ 2

(2) B = H + T

Placing T into (1) and (2) we get:

(3) H = 8 + B ÷ 2

(4) B = H + 8

Using (4) in (3) we get:

    H = 8 + B ÷ 2

(5) H = 8 + (H + 8) ÷ 2

Multiplying (5) by 2 we get:

 2H = 16 + H + 8

 2H = 24 + H

  H = 24

Therefore, by (2):

 B = H + T

 B = 24 + 8

 B = 32

Giving:

 H = 24
 B = 32
 T = 8

And a total of 24 + 32 + 8 = 64 pounds.

Workings

Hint
A little algebra might help.

Answer
¹/₈.

Reasoning
If we convert the question to algebra, we have:
((n^2 + 4) x 2 − 3) x 4 − n = 20

Expanding the brackets and simplifying gives:

(2n^2 + 8 − 3) x 4 − n = 20

    (2n^2 + 5) x 4 − n = 20

         8n^2 + 20 − n = 20

              8n^2 − n = 0 (*)

                8n − 1 = 0

                    8n = 1

                     n = ¹/₈

In the equation marked (*) zero is also a potential solution, but as the question tells us that we "Start with a number larger than 0" we know that n can't be 0, and therefore we can safely divide by n.

Double-Checking
                 ¹/₈
   squared     = ¹/₆₄
   add 4       = 4¹/₆₄
   double      = 8¹/₃₂
   take away 3 = 5¹/₃₂
   times 4     = 20¹/₈

   subtracting ¹/₈ gives 20, as required.

Workings

Hint
Try working backwards.

Answer
148.

148 x 6 = 888.

The easiest way is to divide successive 8's by 6 until you get an integer:
  8 ÷ 6 = 1.3333
 88 ÷ 6 = 14.666
888 ÷ 6 = 148

Workings

Hint
There are 4 possible answers.

Answer
Band, load, lock, and rest, all create new words:

armband and banding
armload and loading
armlock and locking
armrest and resting

Note
Some dictionaries also allow ARMRACK, but others don't. So RACK is a unofficial possible answer.