So basically, you want to show why the two lines (m and n ) are the "same". To show this you would say <4 &<5 are also supplementary because it is the same as <3 & <6. I think this is what the question is asking. To prove this you use the Converse Theorem. Which is what I just showed you with the angles.
It would be 20 percent, I believe. First you would put it into a fraction of 12\60, then you would simplify that into 3\15 then divide as shown. You end up with .2 which would be 20 percent.
