## Geometry: Common Core (15th Edition)

$m\angle EFG=69$ $m\angle GFH=111$
Use the definition of a linear pair: $m\angle EFG+m\angle GFH=180$ Substitute: $(2n+21)+(4n+15)=180$ Combine like terms: $6n+36=180$ Subtract 36 from each side: $6n+36-36=180-36$ $6n=144$ Divide each side by 6: $6n\div6=144\div6$ $n=24$ Substitute to find the measures: $m\angle EFG=2n+21=2(24)+21=48+21=69$ $m\angle GFH=4n+15=4(24)+15=96+15=111$