Correct. The ladder, the wall, and the ground form a right triangle. Let x represent the unknown distance, which is the side adjacent to the $\displaystyle{{75}}^{\circ}\usepackage{cmbright}\Huge\$ angle. You are given the length of the hypotenuse, so you can use cosine to set up an equation:

$\displaystyle{{\cos{{75}}}}^{\circ}=\frac{{x}}{{12}}\usepackage{cmbright}\Huge\$

Solve the equation for x, then use a calculator to find a numerical value:

$\displaystyle{x}={12}\cdot{{\cos{{75}}}}^{\circ}={12}\cdot{0.2588}\ldots={3.105}\ldots\approx{3.1}\usepackage{cmbright}\Huge\$