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

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

What is the riddle which can be asked all day with a different correct answer each time.

John had a bag containing colourful marbles. The colours are red, green and blue. The total number of marbles he had in his bag was 60. There are 4 times as many red marbles as green marbles. 6 more blue marbles than green marbles. How many marbles of each colour did John have?

I hide my treasure in the ground, my tail is big and fluffy. If you spot me in a tree, please don’t call me scruffy. What am I?

Give it food and it will live; give it water and it will die.

I am white when I am dirty, and black when I am clean. What am I?

I’m orange, I wear a green hat and I sound like a parrot. What am I?

A person was found dead on a big green land with no trees or buildings around. When the police arrived, they found a piece of rock lying next to him and the man was wearing clothes comprising of red, blue and yellow colours.

Can you tell who the person is and what was the cause of death?

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?