12 - (x+3) = 10 need the answer fast but i need it right

X= -1 
So first you have to find out which is which. 
So... lets look outside of the parenthesis, you have 12 and 10, and you know your taking something away from 12 which makes 10. 
So right away, i got -1 for x
so the equation would be,   12 - (-1 + 3 ) = 10
Now, Lets use, PEMDAS
p, stands for parenthesis, so, do we have parenthesis?? yes, so we do that first.
-1 + 3 = 2
now we have 12 - 2 = 10
E, stands for exponent, we don't have any exponents so we move on, M, multiply, we don't have anything to multiply, so we skip, D is divide, nothing to divide in this equestion so we skip this step also, A is addition, there are no addition signs, so we skip that step!! Now, We have S  which is Subtraction! we have a subtraction sign, so we have to see if 12-2 DOES equal ten, well my goodness! It does! So the answer is x = -1

Hope i helped. :D