What is 2/5 +1/3= show your work

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]

How to do this , and can some one explain

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)