How can you make number one disappear by adding something to it?

There’s a one-story house in which everything is yellow. Yellow walls, yellow doors, yellow furniture. What colour are the stairs?

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 ?

Irene killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'.

S E Q U E N C _

What does the following represent?

N N N N N N N

A A A A A A A

C C C C C C C

John asked Jack, "The time right now is 7 pm. Can you tell me what will be the time 23, 999, 995 hours later ?"

While Bella does not know the answer, do you ?

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?

Yesterday I fell from 30 feet high ladder but I don't get hurt. Why?

After teaching his class all about Roman numerals (X = 10, IX=9 and so on) the teacher asked his class to draw a single continuous line and turn IX into 6. The teacher's only stipulation was that the pen could not be lifted from the paper until the line was complete.