If 21x = 79x, what is the value of x?

Before the start of the car race, John and Jacob have the same amount of fuel in their car. With this fuel, John can drive for 4 hours while Jacob can drive five hours.
After a time they realize that the amount of fuel left in John's car is 1/4th of the fuel in Jacob's.

For how long they are racing?

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

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?

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.

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

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 ?

Find the number of squares in the below-given picture.

How many triangles are there on the puzzle below?

John was gifted a new Hayabusa. He drove x miles at 55mph. Then he drove x+20 miles at 40mps. He drove his bike for 100 minutes. How much distance did he travel?