What does this Rebus Picture mean?

What does the below rebus riddle means?

Prove that the below maths equation is true.

8 + 8 = 91

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

Can you name some countries which do not have the alphabet 'A' in them?

Can you find a seven digit number which describes itself. The first digit is the number of zeros in the number. The second digit is the number of ones in the number, etc. For example, in the number 21200, there are 2 zeros, 1 one, 2 twos, 0 threes and 0 fours.

Three ants are going up a hill, one behind the other. The last ant then says to the other ants, 'There is an ant behind me!'' How come?

What does this rebus riddle means ?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

2, 3, 5, 9, 17, _ What is the next number in the sequence?