Question

i dont know how to find a .

Answer 1

To find a,construct a line that parallel to AB and DE cutting c, which you could refer to the photo((sorry for my terrible diagram ^^;;

from the photo,we can see that
a= <BCG + <GCE

<BCG=44° (alt.<, AB//FG)
<GCE=20° (alt<, FG//DE)

thus,a= 44°+20° =64°

hope it helps!