27 divided by 10 to the power of negative 5

Need ! give step by step solutions on how to solve number one [tex]\frac{9-2\sqrt{3} }{12+\sqrt{3} }[/tex] number two [tex]x+4=\sqrt{13x-20}[/tex] number three (domain and range) [tex]f(x)=2\sqrt[3]{x} +1[/tex]

Identify an equation in point slope form for the line perpendicular to y=3x+5 that passes through (4,-1)

How can you tell when x and y are not directly proportional?