What is the percent of decrease from 80 to 36

36/80 - 1 = -0.55 = -55%

A decrease of 55%.

δabc ≅ δdcb by sas because

db ≅ ac . . given (side)

bc ≅ bc . . reflexive property (side)

∠dbc ≅ ∠ acb . . alternate interior angles where transversal bc crosses parallel lines bd and ac (included angle)