180°. The answer is 180° because it is a straight line rather than being curved/bent.
Answer:

Step-by-step explanation:
Cosine is the adjacent side over the hypotenuse (You can remember sin, cos, and tan by using sohcahtoa or sin = opposite/hypotenuse, cos = adjacent/hypotenuse, tan = opposite over adjacent). I think a picture would help, too.
I attached a picture of what I think the triangle would look like.
If the picture is right (we're assuming it is) and going with what we're given (the triangle was addressed as triangle XYZ, meaning that <u>angle Y is in the middle and that's the one we'll use</u>).
Looking at my picture then:
.
Answer:
-3x-y=5
y-2z=7
x-4y+z=-9
Step-by-step explanation:
You know how there are 4 different areas in the graph, rotating it 180 degrees from that position will make it be in quadrant 2 (top left). in order to graph the ponts, since it is right across, then you just have to flip the shape around. like how you take a selfe, it flips the capture image around