The number is 7/9
For this problem, let us simply follow the word to build an equation:
The product of a number, n, and -9:
-9n
Is subtracted from the number, n:
n - (-9n)
The result is 7 more than the number, n:
n - (-9n) = 7 + n
So now we simply solve the equation:
n - (-9n) = 7 + n
n + 9n = 7 + n
10n = 7 + n
9n = 7
n = 7/9
Hence the missing number is 7/9.
Cheers.