What begins with T, ends with T, and has T in it?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

What has no start, end, or centre?

In an Art Gallary, When the clock hit 11 am, Artist hung the painting number 30. When it struck 4 pm, he hung painting number 240 and when it struck 7:30 pm, he hung painting number 315.

Can you determine, which painting number will he hang when the time is 9:20 pm?

Why Wine Glass Stem is so long?

John is found dead in his office at his desk. The police have narrowed the suspects down to three people: Mrs. Jacob, John’s wife Hena and his business partner Jason . All three visited John on the day of his murder, but all three provide the police with stories of explanation as to the reason for their visit.
Police found John with his wrist watch still on his right arm, a torn up picture of his wife laying on the floor beside the trash can, and an ink pen in his right hand. On the desk, the police found a name plate, a telephone that was off the hook, and a personal calendar turned to the July 5th page with 7B91011 written on it. After examining this evidence, the police knew their suspect. Who was it ?

Eight of us go fourth, not back, to protect our king from an attack. What are we?

There is something which you can be arrested for attempting but not for successfully completing.

When you say goodbye, I am what you need to tie.
I come as a couple and go wherever you run.
Who am I?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?