First, instead of calling them 'Angle 1-2-3', give them letters.
I take your angle 1 as a, angle 2 as b and angle 3 as c
b 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.