## Geometry: Common Core (15th Edition)

$m\angle A=30$ $m\angle B=60$
It is given that $m\angle A=\frac{1}{2}m\angle B$. $m\angle A+m\angle B=90\longrightarrow$ definition of complementary $\frac{1}{2}m\angle B+m\angle B=90\longrightarrow$ substitution $1.5m\angle B=90\longrightarrow$ combine like terms $m\angle B=60\longrightarrow$ division property of equality Substitute to find $m\angle A$. $m\angle A=2m\angle B=\frac{1}{2}(60)=30$