Let the smaller angle be \(x\). Then, the larger angle is \(x + 18^\circ\).
Since the angles are supplementary, their sum is \(180^\circ\):
\[ x + (x + 18^\circ) = 180^\circ \]
Simplifying:
\[ 2x + 18^\circ = 180^\circ \implies 2x = 162^\circ \implies x = 81^\circ \]
Thus, the smaller angle is \(81^\circ\), and the larger angle is:
\[ 81^\circ + 18^\circ = 99^\circ \]