To solve for the value of x, it is easiest by isolating "x" to one side of the equation. This method is shown below:
-2x - 13 = 8x + 7
Adding 2x to both sides:
-2x - 13 + 2x = 8x + 7 + 2x
-13 = 10x +7
Subtracting 7 from both sides:
-13 - 7 = 10x + 7 - 7
10x = -20
Dividing both sides by 10:
10x / 10 = -20 / 10
x = -2