X/8 - 10 = x/3
bring the values with the variable on one side
x/3 - x/8 = 10
find a common denominator and subtract these fractions
8x/24 - 3x/24 = -10
now subtract fractions
8x - 3x = 5x
5x/24 = -10
multiply both sides by 24
5x = -240
divide both sides by 5
x = -48
the number is -48
Since x=8/3 is a vertical line,the slope is undefined,
I think the answer is letter C
(X+4)(X-4) is the LCD because you just have to look at the denominators and see what factors or values are not already part of your LCD.