Percentage decrease = d
h1 = 2950
h2 = 2550
d/100 = (h2-h1)/h1
d/100 = (2950-2550)/2950
d=13.56
Im pretty sure your answer would be D, 6x
but tell me if im wrong.
Well if you want to turn an improper fraction to a mixed number you just divide the denominator by the numerator if that's what your asking

Alternatively, you can write radicals as rational exponents, so that you get

Then recalling that

, you have