If a sled cost $99.50 what's the mark-up at 95%

If the markup is 95% of the cost, its amount will be
  0.95×$95 = $90.25

The answer is 120. 
We can tell this because the discriminant is equal to b^2 - 4ac. We know a = -2 (the coefficient of x^2), b = 6 (the coefficient of x) and c = 13 (the number on the end). Then we plug in. 
b^2 - 4ac(6)^2 - 4(-2)(13)36 + 8(13)16 - 104120