The sides of similar triangles are proportional, so the ratios of corresponding sides are equal. Corresponding sides will be located opposite corresponding (congruent) angles. For example, the measure of $\displaystyle\angle{Y}\usepackage{cmbright}\Huge\$ equals the measure of $\displaystyle\angle{A}\usepackage{cmbright}\Huge\$ , so XZ does correspond to BC, which is the ratio in the middle. However, the other ratios should also be of lengths in the first triangle to lengths in the second triangle, which they are not.