Which tank will fill first?

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 ?

Can you name any English verb that becomes its past tense by simply rearranging the alphabets ?

What Time Should the last watch show in the below figure?

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?

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

There were two grandmothers and their two granddaughters.
There were two husbands and their two wives.
There were two fathers and their two daughters.
There were two mothers and their two sons.
There were two maidens and their two mothers.
There were two sisters and their two brothers.
Yet there are only six, who are buried here,
All are born legitimate and relationships clear.
How can this happen?

Twenty frogs are sitting on a log floating on the surface of a river. Two of them decide to jump off into the water.

How many frogs are there on the log at this moment?

You need to climb ten stairs. At every stair, you can either take one step up or you can jump two steps up.

In how many different ways you can climb 10 stairs?