Respuesta :

63 By definition.  Actually 1,2 and 3 are equal to each other since a is parallel to b.
∠2=∠3 because they are oposite angles (or something like that)

so
if ∠2=63°  and ∠2=∠3 then
∠3=∠2=63°

∠3=63°


answer is first option