If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Find out the missing number in the picture attached:

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

How do you go from 98 to 720 using just one letter?

Can you find out which number multiplied by itself will give the output as 12345678987654321?

Our product and our sum always give the same answer. Who are we?

Using Only Five 5's and any mathematical operator make sum as 37

Replace all '*' with digits 1, 2, 3, 4, 5 and 6 to make below statement true.

* *
x *
=====
* * *

Use the numbers 2, 3, 4 and 5 and the symbols + and = to make a true equation. Conditions: Each must be used exactly once and no other numbers or symbols can be used.