Insert a digit to make numbers that are divisible by 6 if it is possible: 531__0

Numbers are evenly divisible by 6 if they are evenly divisible by both 2 and 3. Even numbers are always evenly divisible by 2. Numbers are evenly divisible by 3 if the sum of all the individual digits is evenly divisible by 3. For example, the sum of the digits for the number 3627 is 18, which is evenly divisible by 3 but 3627 is an odd number so the number 3627 is not evenly divisible by 6.

For a number to be divisible by 6, the last digit of the number has to be even or 0, and the digits of the number have to add up to a multiple of 6.

Last digit - 0

5+3+1+0=9

Closed multiple to 6 is 12.

12-9=3

3 is the missing digit.