The two numbers that have a tens digit that is eight more than the ones digit are 80 and 91. Note that there are some larger numbers that also exhibit this pattern, such as 180, 280, 191 or 291.
The ones digit and tens digit are both examples of place values. Each column in a number to the left or right of the decimal has a place value. If there is a one in the tens column, it represents one set of 10. Likewise, if there is a two in the hundreds column, it represents 2 sets of 100, or 200 total.