[tex] \frac{3x}{4} = 7-\frac{x}{3}
[/tex]
[tex] \frac{3x*3}{4*3} = \frac{7*12}{12} -\frac{x*4}{3*4}
[/tex]
[tex] \frac{9x}{12} = \frac{84}{12} -\frac{4x}{12} [/tex]
[tex]12*( \frac{9x}{12} = \frac{84}{12} -\frac{4x}{12} )[/tex]
[tex]9x=84-4x
[/tex]
[tex]13x=84[/tex]
[tex]84/13[/tex]
