Hello there!
15 is a term so the first digit in the code is 4.
15-3y is an expression so the second digit in the code is 5
4 5 x x x is the code right now
Now, let's solve the third puzzle:
4(2y-3)-2y=24
8y-12-2y=24
Combine like terms:
6y=36
x=6
4 5 4 x x is the code right now
The next problem:
1/3(12x-3)=7
4x-1=7
4x=8
x=2
4 5 4 2 x is the code right now
Problem 5: I think it's infinite solutions
4 5 4 2 4 is the code!
I hope it is correct! If it isn't, don't report and send me more puzzles! I would love to strain my brain!
Your friend, 
I think it's 1 3/4. I had one similar earlier.
Answer:
You have 2 and 1/2 pizzas and your friend has 5/6 of a pizza.
Step-by-step explanation:
You have 3 1/4 pizzas. If you get rid of 3/4 of a pizza, you will end up with 2 2/4 pizzas.
To make it easier, you can just change the values into improper fractions: 3 1/4 = 13/4
13/4 - 3/4 = 10/4
10/4 = 2 2/4 pizzas
(2 2/4 = 2 1/2)
Anyways! You now have 2 and a half pizzas. You have 3 times the amount of pizza that your friend has. In other words, your friend has 1/3 the amount of pizza that you have. You can solve for this in two ways, whichever way you solve it is up to you.
- You can solve this problem by dividing the amount of food you have by 3:
which equals 0.8333... (the 3 is repeating). But you can just keep your final answer in fraction form if you want to: 
- You can solve this problem by multiplying 1/3 to the amount of food you have:

You have 2 and 1/2 pizzas and your friend has 5/6 of a pizza.
Answer:
3/4, and 6/8
Step-by-step explanation:
3/4 = 9/12 simplfied
6/8 = 3/4 times two
3 percent i think just double check