Explanation:
Only 1 number works. 1 will make 819 which is divisible by 9.
Since it is 1 of ten numbers can go in the blank, the answer is 1/10 which is 0.1
The 10 number choices are
0,1,2,3,4,5,6,7,8,9
The only one that works is 1 as I've stated.
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