Every words stands for unique digit that makes the arithmetic equation true

SEVEN + SEVEN + SIX = TWENTY.

What are the digits ?

I can write cow in 13 letters.

Can You?

Can you find the largest Three-digit number whose sum is 14 and whose square is less than 5,00,000?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

If,

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

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

D + F = ?

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

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?

Which tank will fill first?

There is a hypothetical state between the USA and Mexico border 'Tango'.
Here 70 percent of the population have defective eyesight, 75 percent are hard of hearing, 80 percent have Nose trouble and 85 percent suffer from allergies, what percentage (at a minimum) suffer from all four ailments?