Answer:
x = 0
or
x = (-9)
Explanation:

transfer like terms to the same side of the equation

Add/subtract like terms

Now we can factor terms

we can write them with their common divisor
x*(9+x) = 0 for this equation to be correct either x = 0 or (9+x) = 0
if x = 0 well then that's the first value of x
if (9+x) = 0 then x = -9 and this is the second value of x