To solve, use properties of logs, specifically log(u)+log(v)=log(uv). This makes your equation logb(x+1)+logb(x-8)=logb((x+1)(x-8)), which can be made into logb(x^2-7x-8) by expanding the factored form.
The answer is 9
both 81 and 63 are dividable by 9, and nothing higher
The numbers 0, 1, 2, 3, 4 could all be the missing digit because they're all numbers that round down. hope this helped!
