Answer:
C. The length of one lap.
Step-by-step explanation:
In the first four words, the problem statement tells you that L is <em>the number of laps run</em>. It is not the length of one lap.
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<em>Comment on the problem presentation</em>
Appropriate punctuation would be very helpful. Apparently, it is a 1/4-mile track, not a 14-mile track. Apparently, the distance is 1 1/2 miles, not 112 miles. Copying and pasting problem text often leaves out the special symbols used on some web sites. Some editing is usually needed.
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