9.
a)
[tex]xy = k \ \ /:y\\\\\underline{x = \frac{k}{y}}[/tex]
b)
[tex]4x+2y = 6\\\\4x = 6-2y \ \ /:4\\\\\underline{x = \frac{6-2y}{4}}[/tex]
c)
[tex]\frac{a+b}{x} = 3 \ \ /\cdot x\\\\3x = a+b \ \ /:3\\\\\underline{x = \frac{a+b}{3}}[/tex]
