Incorrect. To use the substitution method, solve the top equation for C by subtracting 2D from both sides, to get $\displaystyle{C}={4.35}-{2}{D}\usepackage{cmbright}\Huge\$ . Now substitute this expression for C in the bottom equation. Your new equation is $\displaystyle{2}{\left({4.35}-{2}{D}\right)}+{3}{D}={7.45}\usepackage{cmbright}\Huge\$ . Can you solve this equation for D?