He can make 12 or 9 because 9x4=36 and 12x3=36
Do you have the answer options? Sorry, can't answer without them ):
-6 +8x = -38
8x = -32
x = -4
I did this by first adding 6 to both sides to get 8x by itself. I then divided by 8 to get x by itself. I remembered to use the - - + rule (Two negatives make a positive, a positive and a negative make a negative). Hope this helps!

This is found by the volume of a cone formula

Where b is the base and h is the height

First, we can factor this to make it easier to solve:
3(x^3 + 13x^2 + 13x + 9)
Now, we can use the rational root theorem like so:
List factors of 9:
1, 3, 9.
List factors of 1:
1
Because of this, we know our possible rational roots are:
+/-1, +/-3, +/-9
If none of these zeros fit using the remainder theorem, then we know our roots will be irrational.