I AM A BOX OBJECT USED TO WRITE LETTERS AND NUMBERS WHO AM RI RIDDLES WITH ANSWERS TO SOLVE - PUZZLES & BRAIN TEASERS

A boxer knows his blows; a person with a cold blows his nose. Did you answer this riddle correctly?
YES  NO  

Because the box said: "Tear Along Dotted Line." Did you answer this riddle correctly?
YES  NO  

There are 11 letters in "THE ALPHABET." Did you answer this riddle correctly?
YES  NO  

A clock! Did you answer this riddle correctly?
YES  NO  

Ring Did you answer this riddle correctly?
YES  NO  

The paperboy. Did you answer this riddle correctly?
YES  NO  

A coffin Did you answer this riddle correctly?
YES  NO  

The word 'what' has 4 letters in it, 'yet' has three, 'sometimes' has 9, 'then' has 4, 'rarely' has 6, and 'never' has 5. Did you answer this riddle correctly?
YES  NO  

Startling - starting - staring - string - sting - sing - sin - in - I. Did you answer this riddle correctly?
YES  NO  

Alone.

Behead me and I am Lone.
Behead me again and I am One. Did you answer this riddle correctly?
YES  NO  

Sugar Did you answer this riddle correctly?
YES  NO  

A cereal killer. Did you answer this riddle correctly?
YES  NO  

Post Office Did you answer this riddle correctly?
YES  NO  

The number missing on the left is 8 and the one on right is 7.

Explanation:
The pattern:
The number in the center of triangle is the square root of the sum of the numbers sitting outside on the corners.

Thus,
10 + 22 + 4 = 36
Square Root of 36 = 6

In the same manner:

10 + 42 + 12 = 64
Square Root of 64 = 8

12 + 22 + 15 = 49
Square Root of 49 = 7 Did you answer this riddle correctly?
YES  NO  

Only one, it's no longer empty after the first Did you answer this riddle correctly?
YES  NO