Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

Krish is 45 years old and his mother Crishtina is 73 years old.

Can you find out how many years ago, his mother was three times his age?

Find out a multi-digit number that if multiplied by the number 9 or any of its multiplications products (i.e. 18, 27, 36, 45,..) will result in the multiplication factor repeated (n) number of times.

By using all numbers, i.e. 123456789 and subtraction/addition, operators number 100 can be formed in many ways.
Example: 98 + 7 + 6 - 5 - 4 - 3 + 2 - 1 = 100

But if we add a condition use of the number 32 is a must. Then there are limited solutions.
One of such solution is: 9 - 8 + 76 + 54 - 32 + 1 = 100

Can you tell me any other solution?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

In a stable, there are men and horses. In all, there are 22 heads and 72 feet. How many men and how many horses are in the stable

Can you write down eight eights so that they add up to one thousand?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?