Respuesta :

eagerreader
∡DBE=90-∡EBF=90-51=39°
      ∡DBE and ∡EBF must add to 90 because ∡DBF is vertical from ∡ABC a 90° angle

∡GBC is 39°
      ∡GBC is vertical to ∡DBE; verticla angles are =

Angles on a line add to 180°. Subtract the measure of ∡ABC to find meausre of ∡ABD