To find the distance between the two cars, we need to solve the equation 8x - 12 = 4x.
Subtract 4x from both sides to isolate the x term:
8x - 4x - 12 = 4x - 4x
4x - 12 = 0
Now, add 12 to both sides to get the x term alone on one side of the equation:
4x - 12 + 12 = 0 + 12
4x = 12
Finally, divide both sides by 4 to solve for x:
4x / 4 = 12 / 4
x = 3
So, the distance between the two cars is x = 3 miles. Therefore, the correct answer is:
x = 3 miles.