Replace the question mark with the number below given a simple math problem.

By removing one matchstick and adding one matchstick, can you convert the word "ZOO" to an animal name?

A blonde put eyeliner on her head. Why?

In a contest, four fruits (an apple, a banana, an orange, and a pear) have been placed in four closed boxes (one fruit per box). People may guess which fruit is in which box. 123 people participate in the contest. When the boxes are opened, it turns out that 43 people have guessed none of the fruits correctly, 39 people have guessed one fruit correctly, and 31 people have guessed two fruits correctly.
How many people have guessed three fruits correctly, and how many people have guessed four fruits correctly

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

I am 5 letters long.
My first two tell you who I am
My first 3 could be a medicine
My last three reversed could be a young boy.
My 4th, 3rd and 2nd in that order could be a fruit drink.
If you have me you may hang me round your neck
WHAT AM I ?

They are three errirs in this question. Can you find them?

If,
9 * 8 * 7 = 65
8 * 7 * 6 = 50
7 * 6 * 5 = 37

Find
6 * 5 * 4 = ?

You can hear me, but you can't touch or see me.

What am I?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.