I believe the answer is C.
Answer:
48
To start you will find the area as if it was a rectangle. To do that you have to do 8x12. 8x12 = 96, but to find the area of a triangle you take the area of the rectangle and divide it by 2. 96 divided by 2 is equal to 48.
There are other methods of solving this but I think this is the easiest way!
First Step: Leave "x" alone, pass the 3 to the other side
X= 10+3
Second Step: Add 10 plus 3
X= 13
So your answer is: x=13