Solution:

2 minutes (duration between 9:59 and 10:01)

Solution:

Blue could only be wearing white or red and we know that there is already someone else wearing the white shirt so Mr. Blue could only be wearing the red shirt.

Mr. White could have only been wearing a blue or a red shirt, and red is already taken, so Mr. White is wearing a blue shirt.

Mr. Red now has to be wearing a white shirt.

Solution:

charles put the ring into the box, secure it with one of your locks, and send the box to the girl firend.
She should then attach one of his own locks and return it. When you receive it again, remove your lock and send it back with her lock. Now she can unlock his own lock and retrieve the object.

Solution:

13 + 11 + 6 = 30

Explanation
The trick is that you just need to rotate '9' to form '6'.

Solution:

A
D
C
A
B

Solution:

888 + 88 + 8 + 8 + 8 = 1000

Solution:

2100 miles.

Each vowel equivalent to 500 and each consonant equivalent to -200

Solution:

The brain teaser can be solved as shown in the image below.

Solution:

The Lady sitting in the chair has the detector attached to the back of her blouse.

Solution:

The clerk said that every day the password is CHANGED. Changed is the password.

Solution:

Hhe hung herself using big Ice slabs , which are now now melted and hence puddle of water.