Congruent triangles must be the same size and shape. These two triangles have the same shape, but $\displaystyle\Delta{D}{E}{F}\usepackage{cmbright}\Huge\$ has a larger size, so the triangles are not congruent. The correct answer is $\displaystyle\Delta{A}{B}{C}\usepackage{cmbright}\Huge\$ ~ $\displaystyle\Delta{D}{E}{F}\usepackage{cmbright}\Huge\$ because $\displaystyle\frac{{4}}{{6}}=\frac{{5}}{{7.5}}=\frac{{6}}{{9}}\usepackage{cmbright}\Huge\$ .