Question

Given EFGH and E=45°, what is the measure of angle F?

Answer 1

Opposite angles are congruent and adjacent angles are supplementary.

so < E + < F = 180...and < E = 45
45 + < F = 180
< F = 180 - 45
< F = 135 <==

Answer 2

Remember that opposite angles are congruent. 

So,

we know that <E= <G

That is 45+45= 90 degrees 

We also know that consecutive angles are supplementary. E and F would equal 180 degrees. 

180-45=135

<F= 135 degrees. 

We can check this by seeing if all the angles add up to 360 degrees/

135+135+45+45

=360 <== this works

I hope this helps!
~kaikers