## Geometry: Common Core (15th Edition)

$m\angle ABC=45$ $m\angle DBC=34$
Angle Addition Postulate: $m\angle ABC + m\angle DBC =m\angle ABD$ Substitute the given values. $(8x-3)+(5x+4)=79$ Solve for x. Combine like values. $13x+1=79$ Subtract 1 from each side. $13x+1-1=79-1$ $13x=78$ Divide each side by 13. $13x\div13=78\div13$ $x=6$ Substitute for x to find $m\angle ABC$ $m\angle ABC=8x-3=8(6)-3=48-3=45$ Substitute for x to find $m\angle DBC$ $m\angle DBC=5x+4=5(6)+4=30+4=34$