300 is the number I choose, the easiest way to find the number that is 10 more than 300 is by adding 10, but I think that the answer you're looking for is to add 1 to the digit in the tens place. Ex: 300 + 10 = 310 or
.3.0.0 - the original number
.0.1.0 - adding the number one in the tens place
310 - the answer.
I hope that this helped!