Using Only Five 5's and any mathematical operator make sum as 37

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

How do you go from 98 to 720 using just one letter?

How many triangles are there on the puzzle below?

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

You are given a cube that is made with the help of 10x10x10 smaller cubes summing up to a total of 1000 smaller cubes. You are asked to take off one layer of the cubes.
How many remain now?

A man always keeps a spare tyre in his car. To make full use of all the five tyres, he changes the tyres in a manner that for a distance of 1, 00,000 km, each of them runs the same distance.

Can you calculate the distance travelled by each tyre on that journey?

Three friends decide to distribute the soda cans they had among them. When all of them had drunk four cans each, the total number of cans that remained was equal to the cans each one of them had after they had divided the cans.

Can you calculate the total number of cans before distribution?

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

If "P" means "-", "Q" means "/", "R" means "+", and "S" means "*" then find the value of the following:

21 Q 7 R 9 S 10 P 13