A straight line (180o) is still an angle. Would you be wondering if the question said "Can 179o be a real angle?" No you would simply draw it. 1 degree more and you have 180o and it is an angle as well.
So you have a line that is both a line and an angle with A in the middle.
To determine the cost of each meter of the ribbon, we divide the cost for 5 meters of ribbon by 5. That is,
x = $4 / 5
where x is the cost of each meter. Simplifying will give us an answer of $0.8/m. Converting this to per mm.
($0.8/m) x (1 m/ 1000 mm)
= $0.0008/mm
We can simplify across between the 5 and the 50 and also between the 42 and the 3.