Why are all black people so quick ?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

How many times can you subtract the number two from the number fifty?

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

A man in a car saw a Golden Door, Silver Door and a Bronze Door. What door did he open first?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

How many bananas can you eat if your stomach is empty?

Mr Black, Mr Gray, and Mr White are fighting in a truel. They each get a gun and take turns shooting at each other until only one person is left. Mr Black, who hits his shot 1/3 of the time, gets to shoot first. Mr Gray, who hits his shot 2/3 of the time, gets to shoot next, assuming he is still alive. Mr White, who hits his shot all the time, shoots next, assuming he is also alive. The cycle repeats. If you are Mr Black, where should you shoot first for the highest chance of survival?

Where do fish keep their money?

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?