Question

Letters a, b, c, and d are angle measures. Which should equal 105° to prove that f ∥ g?
abcd

Answer 1

we know that

If lines f and g are parallel

then

the angle c must be equal to

∠c=$75\°$ ------> by alternate exterior angles

and

∠c+∠d=$180\°$ ------> by supplementary angles

so

∠d=$105\°$

therefore

the answer is

The angle d should be equal to $105\°$ to prove that f ∥ g

Answer 2

your answer is d on edge.