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

What is next number in the pattern below:

131 517 192 123 ?

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

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

Can you find the ages of a son, father and grandfather based on the following facts?
The sum of the ages of grandfather, father and son is 140 years.
The age of the son in months is the same as the grandfather in years.
The age of the son in days is the same as the father in weeks.

Find out the missing number in the picture attached:

Three brothers Jacob, John, and James live in Mexico City. The product of the ages of these brothers is 175. Jacob and John are twins. How old is James?

Can you find out which number multiplied by itself will give the output as 12345678987654321?

John drives to his office at 20km/hr. After reaching the office, he realizes that today is a holiday. He went back at an average speed of 30km/hr. Discounting the time spent in the stoppage what was the average speed of his journey?

Use the numbers 2, 3, 4 and 5 and the symbols + and = to make a true equation. Conditions: Each must be used exactly once and no other numbers or symbols can be used.