Why is the Hole below a Lock?

Can you solve the below algebraic mathematical equation?

(J+O+I+N+T)3 = JOINT

A clock loses 10 minutes each hour. If the clock is set correctly at noon, what time is it when it reads 3 PM?

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

If,

A + B = C
D - C = A
E - B = C

Based on the above equations, find out the answer for:

D + F = ?

Bay of Bengal is in which state?

What is the below Rebus indicate?

Known by all without exception, Forever here, for your protection, Sometimes strong, sometimes weak, Right after the night I come - hot and chic. And while millions of miles away, I always get to you, I find my way. No life around could do without me, Can you guess what I might be?

What word is identified by the below rebus?

Your Your Your Your Your
Your Your Your Your Your

A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?