## Prealgebra (7th Edition)

The supplement is $75^{\circ}$
Two angles are supplementary if they add up to $180^{\circ}$. This means we have to find $\angle A$, where: $105^{\circ}+\angle A=180^{\circ}$ $\angle A=180^{\circ}-105^{\circ}$ $\angle A=75^{\circ}$