From 1 to 99, there are 99 numbers.
The first nine of them ... 1 through 9 ... have only one digit, so discard them.
So there are (99 - 9) = 90 positive whole numbers with 2 digits.
And another 90 negative whole numbers with 2 digits.
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Number of 7 digit combinations out of the 10 one-digit numbers = 120.
There are 5! = 120 such numbers.
There are 90,000 such numbers.
8100
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