Solution:

There are multiple solutions to the brain teaser.

1) 11+13+3! = 30
2) 11.5+5.5+13 = 30
3) 11+13+6(rotating 9)... my favorite.

Solution:

A = 7 , B =1 and C = 0

Explanation:
0 3 7
+ 7 3
=====
1 1 0

Solution:

It can be done as shown below.

Solution:

100

Solution:

3

Explanation:
The logic used to decipher the equation : Sum the numbers and then subtract the two digits to get the desired answer.

09 + 11+ 13 => 33 => 3 - 3 => 0
12 + 14 + 17 =>43 => 4 - 3 => 1
22 + 25 + 28 =>74 => 7 - 5 => 2
31 + 32 + 33 => 96 => 9 - 6 => 3

Solution:

49502 +
45634
=====
95136
=====

Solution:

0(zero) off course.

Solution:

450

Explanation:
II - IV + IX = 200
=> VII = 200

VI + I - V = 100
=> II =100

II - VI + VII = 150
=> III = 150

Therefore,
VII + II + III = 200 + 100 + 150 = 450

Solution:

18 * 12 / 6 + 4

Solution:

1611

Explanation:
The number on the right side is formed as (sum of digits of the 1st number)(number1/number2)
example,
24 $ 6 = 64 (2+4 = 6) (24/6 = 4)
35 $ 5 = 87 (3+5=8) (35/5 = 7)
63 $ 7 = 99 (6+3 =9) (63/7 =9)

Simillarly,
88 $ 8 = (8+8 = 16) (88/8 = 11)