Logain Potpourri VI

I) Easy Math: Take 2?

Given the following, what is the missing integer value?

81x5/628/35x609/?/7 = 126

II) A Verified Connection

Meat
Agent
Submarine
Lantern
Shield
Girls
?

(5-3, 3-3, 7-6, 4-2, 2-3) = ?

III) Modern Alchemy

Coming across a recipe for turning lead into gold, you try and follow the given instructions you found in a book. There are handwritten notes that say "something is wrong, this recipe holds no water." You decide to give it a try anyway...does it work at all?

Using your basic black cauldron full of lead to start, melted down of course….

Add the bone of a short loin, a pinch of salt,
Mix thoroughly with water and you’ll find no fault.
Remove the heat and just let it simmer a touch,
Add half of a fairy wing and cinnabar, but not too much.
Add a drop of arsenic, can you begin to feel the power?
Add brimstone and quicksilver and close the lid for an hour.
Open pot to release the chaos, and you’ll emit flashing rays,
Stir up the remainder of the mix and let settle a ways.
The ingredients are complete, the spell finished and cast,
If you look at the result, you should have gold now at last.

IV) Limited Access

Trying to break into a lab, you find that there are 4 scientists who have security access codes. An informant has discovered the four scientist’s codes, and they are as follows:
#1) 7-5-3, #2) 8-2-5, #3) 6-9-0, #4) 9-2-1.

You sneak into the building and knock out one of the scientists…but you don’t know which one. You watch for the other three to enter the lab to observe their security codes, so that you can enter the one for the man you disabled. But, unfortunately for you, you watch in horror as the three scientists enter the lab using the following security codes:
1-1-4-3-1, 3-2-2-2-1, 2-2-3-2-1.

You try to rationalize what went wrong as you approach the security pad. You know your informant would not give you false information. Oddly, your informant mentioned the complete list of codes he saw never went above a 3 digit number, yet the security pad appears to allow for numbers up to ten digits. Also, more curious is that while numbers 1-9 are there, the pad lacks a 0 key. Is it possible that you should still know the code?

Image by Courk.