Answer:
4
Step-by-step explanation:
The mean of 2x and 12 is (2x+12)/2, so we get the equation:
(2x+12)/2 = 10 =>
x+6=10
x = 10-6 = 4
* Your question states four numbers, but you write only two... the answer could be wrong because of that.
(-3) - (-6) = -3+6 = 6-3 = 3
If you don't know how to divide polynomials then I can help with that too or you can just search it up