Incorrect. Try setting up the problem like this:

	Earnings	=	Rate	*	Number sold
Earrings	e	=	6	*	n
Necklaces	$\displaystyle{232.50}-{e}\usepackage{cmbright}\Huge\$	=	7.50	*	$\displaystyle{36}-{n}\usepackage{cmbright}\Huge\$

Which leads to this system:

$\displaystyle{e}={6}{n}\usepackage{cmbright}\Huge\$

$\displaystyle{232.50}-{e}={7.50}\cdot{\left({36}-{n}\right)}\usepackage{cmbright}\Huge\$

Solve for the variable n. The easiest way to do this is to substitute $\displaystyle{e}={6}{n}\usepackage{cmbright}\Huge\$ into $\displaystyle{232.50}-{e}={7.50}\cdot{\left({36}-{n}\right)}\usepackage{cmbright}\Huge\$ , resulting in $\displaystyle{232.50}-{\left({6}{n}\right)}={7.50}\cdot{\left({36}-{n}\right)}\usepackage{cmbright}\Huge\$ . Then solve for n.