What does this mathematical rebus means ?

Solve the following series:
AZ, GT, MN, __, YB

I have branches, but no fruit, trunk or leaves. What am I?

With the help clues provided in the image, can you find the 5 digit key?

What Does this text mean:

important=important

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?

What breaks yet never falls, and what falls yet never breaks?

Trying to tease Birbal, Akbar gave him one gold coin and ask him to buy
* something for him to eat
* something for him to drink.
* something to feed the cows
* something to plant in the garden
and most important you need to buy only one thing.

What must Birbal buy to silence Akbar?

Can you complete the sequence puzzle?

AR TA GE CA LE VI LI _

A mother is 21 years older than her child. In exactly 6 years from now, the mother will be exactly 5 times as old as the child.
Where's the father?