[tex]a.\\g=\frac{w}{m}\ \ \ \ |multiply\ both\ sides\ by\ m\neq0\\\\w=gm\ \boxed{c.}\\\\therefore:\boxed{a.}\ is\ equivalent\ to\ \boxed{c.}\\\\b.\\g=\frac{m}{w}\ \ \ \ |multiply\ both\ sides\ by\ w\neq0\\\\gw=m\ \ \ \ |divide\ both\ sides\ by\ g\neq0\\\\w=\frac{m}{g}\ \boxed{d.}\\\\therefore:\boxed{b.}\is\ equivalent\ to\ \boxed{d.}[/tex]