The measure of a supplement of an angle is 12° greater than three times the measure of a complement. How do you find the measure of the angle?

The angle is ${51}^{o}$
$180 - a = 12 + 3 \cdot \left(90 - a\right) \implies 180 - a = 12 + 270 - 3 a \implies 2 a = 102 \implies a = 51$