using four eights (8) and a one (1) and one mathematical symbol , create the number 100

Imagine you are in a room with no windows or doors. How will you get out?

If eleven plus two equals one, what does nine plus five equal?

Make the seating arrangement of 10 children in such a way that there are 5 rows with 4 children in each row.

I am thinking of a five-digit number such that:
The first and last digits are the same, their submission is an even number and multiplication is an odd number and is equal to the fourth number. Subtract five from it and we obtain the second number. Then divide into exact halves and we get the 3rd number.

What number I am thinking of?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

Doctor Alex and a bus driver John are both in love with the same woman named Olivia. The bus driver need to go for a long trip of 10 days, Before he left he gave Olivia 10 apples.

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.