What is 6789 rounded to the nearest ten

Pls i’m too dumb to know what i’m doing right now

Given the function f(x) = log base 4(x+8) , find the value of f^-1(2)

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