alright, all numbers that are in the 300 start with a 3, that's 100 numbers
hold a sec, it said 'or' not 'and', so we have to exclude those that start and end with a 3, like 303 and 313. that is 10 of them
in every hundred, there are 10 numbers that end with a 3 (the ones like 3,13,23,33,43,53,63,73,83,93)
so from 200 to 300, there are 10 of those
from 300 to 400 there are 10, wait we said 'or' so nope
100-10+10
so 100 numbers
if you are allowed to include numbers that start and end with 3 (like 303), then there are 120 numbers