The first question probably has a drawing that is not included. Can you please include whatever drawing cam with it?
The Qeustion 2:
starting with writing the complementary angles:
The angles <a and <b being complementary means that
<b = 180 - <a
The angles <b and <c are complementary - that means
<c = 180 - <b
now plug in the first equation for <b to get:
<c = 180 - (180 - <a) = 180-180+<a= <a
so
<c = <a
which was to be proved!