Random Puzzles 

Workings

Hint
There is only one way to make the middle 25.

Answer
 

Workings

Hint
Start by filling the 9 gallon container, and then use that to fill the 4 gallon container.

Answer
Here are the contents of the containers after each stage:
A   B
9   0      fill A
5   4      fill B from A
5   0      empty B
1   4      fill B from A
1   0      empty B
0   1      fill B from A
9   1      fill A
6   4      fill B from A
6   0      empty B

This leaves 6 gallons in container A.

Workings

Hint
The first 5 words begin with D, A, E, W, T.

Answers
--lta = delta --yss = abyss --pty = empty --dth = width --day = today --ybe = maybe --dex = index or codex --fth = fifth --nda = panda --aph = graph --alp = scalp --era = opera --njo = banjo --eue = queue --xty = sixty

Workings

Hint
A little bit of algebra might help.

Answer
I asked for 7 feet, 4 inches and Alex brought me 4 feet, 7 inches.

Reasoning
If we label what I asked for as A feet and B inches, which is (12 x A + B) inches, then I actually received B feet and A inches, which is (12 x B + A) inches. Which means that:

   ⁵/₈ x (12 x A + B) = (12 x B + A)

Simplifying gives:

   A = ⁹¹/₅₂ x B

As B is the number of inches, it can only be between 1 and 12 and must give A as a whole number of feet.

B = 4 is the only possible value, which means that A = 7.

So I originally asked for 7 feet, 4 inches.

Double-Checking
I received 4 feet, 7 inches = 55 inches.

I asked for 7 feet, 4 inches = 88 inches, and 88 x ⁵/₈ = 55.