(30 points) which answer does not show a direct variation between x and y? a) y=5xb) y=6/xc) y=0.7xd) y=x/9

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]

Asap! i'm not good math and i'm lost.

3x + 4y = 5 x- 3y = -7 solve by substitution