ALG2 PRONLEM HELP !! ASAP ! 10 POINTS?

First digit can be 1-9, so that's 9 possibilities. Second digit can be 0-9, except for what the first digit is, so that's 9 more possibilities. From there, 3rd digit, 8 possibilities; 4th, 7; 5th, 6;, 6th, 5; and 7th, 4. That's 9x9x8x7x6x5x4 = 544,320. If you can repeat the digits, then it's 9 x 10^6 (you can use any of the numbers from 0-9 for the last 6 numbers), which is 9 million.