First, instead of calling them 'Angle 1-2-3', give them letters.

I take yourangle 1asa,angle 2asbandangle 3ascb and c are complementary. This means b + c = 90

And the question gives us a + b = 90

c = 90 - b

a = 90 - b

Hence, a = c.

I couldn't understand the 2nd question. Please make it clear and draw it.