You have to read the protractor to determine the measure of each angle.
For all the angles B is the vectress.
∠ABF =90º
∠ABE= 40º
∠ABD= 20º
∠EBF= ∠ABF-∠ABE= 90º-40º= 50º
∠DBE= ∠ABE-ABD= 40º-20º=20º
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