Can you find out the missing number?

? 4 5 3 5

9 5 7 10 3

John was working on a Chemical Mixture whose weight comprise 90% liquid and 10% solid. The total weight of the mixture is 20 pounds. After a while, John noticed that some of the liquid evaporated and now the liquid comprises just 50% of the weight.

What is the weight of the chemical mixture now?

Can you replace the question mark with the correct number in the below table sequence?

Make a sentence consisting of three words that have the whole alphabet.

Living above a star, I do not burn
Eleven friends and they do not turn
I can just be visited in a sequence, not once or repeatedly
PQRS are my initials
Can you tell my name accurately?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Can you name some countries which do not have the alphabet 'A' in them?

I am first found in caves, now prolific online; I am a depiction, a drawing, a symbol, or sign. I will convey whichever mood you could wish; or for that matter, a fist, flask, or fish. What am I?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

Whats the next number in the below number sequence pattern.