Solution:

As we have been informed that the prices are a full dollar increment, this eases out the situation.

If we look at the price of pineapple and capsicum, we can easily make out that both of them are priced $1.
This is because the price has to be at least $1 and since both of them costs $2 together, they must cost $1 separately.

Solving the rest of the question is child’s play. You have to use simple mathematics.

For an instance:
Jalapeno + Pineapple = $5
Now, we know that pineapple costs $1. Thus,
Jalapeno + $1 = $5
Jalapeno = $4

You can find out the price for each one of the toppings in a similar fashion.
Capsicum $1
Pineapple $1
Mushrooms $3
Corn $2
Jalapeno $4
Red Pepper $2
Black Pepper $3
Olives $4

Solution:

20741616380

Explanation:
5 * 5 - 5 =>20
20 * 20 - 20 => 380
380 * 380 -380 =>144020
144020 * 144020 - 144020 => 20741616380

Solution:

1

Explanation:
4 + 9 = 1
The trick to solve is to assume the first number as the time in AM and the second number is the number of hours you have to add to it. You'll find the time in PM when you do that.

For example
7 AM + 7 hours = 14:00 or 2 PM

4 AM + 9 hours = 13:00 or 1 PM.

Solution:

"World War I" was named after after "World War II"

Solution:

common sense

Explanation :
We can break it into the following three parts
ITIT
,N
CENTCENT

Now ITIT = 2 Its which can be molded into IT's
,N = Comma + N which can be molded into Common
CENTCENT = 2 Cents which can be molded into Sense

So, the letters basically represent:
It's common sense.

Solution:

Were you able to do it under two minutes? The words that will be formed are as below:
Friend
Society
Alien
Stymie
Shriek

Solution:

The murderer is Marcus.

The notes hinted towards the name of Marcus. How?
Just take the first letter from Compound, Art Room, Restroom, Underwater Room, Study Room and Movie Room and you will get:

C, A, R, U, S and M.

Rearranging these words leads to the name Marcus who is the murderer.

Solution:

She was not able to find 11 on phone.

Solution:

The driver is actually the wife and mother.

Solution:

The next number is 392.

The first number = (Square of 1 + Cube of 1)
The second number = (Square of 2 + Cube of 2)
The third number = (Square of 3 + Cube of 3)
The fourth number = (Square of 4 + Cube of 4)
The fifth number = (Square of 5 + Cube of 5)
The sixth number = (Square of 6 + Cube of 6)
Therefore, the seventh number will be
Square of 7 + Cube of 7 = 392.