Answer:
35
Step-by-step explanation:
We know that the numbers have to be in ascending order. If, for example, the first digit is 0, and second digit is 1, then we would have 5 other numbers in the ones place that would be larger. If the second digit is 2, then would would have 4 other numbers that would be larger, and so on. So if 0 is the first digit, then we would have 5+4+3+2+1=15 combinations. If 1 is the first digit, then we would have 4+3+2+1 combinations. Eventually, we would get 35.
