what does the below math rebus puzzle mean?

A brand new Mobile Phone was on sale at 20% as a promotional offer. By what per cent must the Mobile price be increased to sell it at the original price again?

Which is Odd One Out and why?

4377

3954

9862

8454

9831

Open a Laptop which is password protected. Hint for the password is given as below:

1 mobile 3 books 2 Boards 1 night 4 balls 2 lighters 1 ghost 1 hat 3 watches

In particular commonwealth games, a female participant won silver and gold medals for a single event.

How can this be possible?

I cannot talk, but I always reply when spoken to. What am I?

There are 3 apples in the basket and you take away 2. How many apples do you have now?

Why do we preferably have round manhole covers and not square ones?

You’ll find me on Mercury, Earth, Mars, Jupiter, Saturn, and Uranus. But never Neptune, or Venus. What am I?

No matter how little or how much you use me, you change me every month. What am I?