Step-by-step explanation:
To calculate a slope, we need to apply: 
Applying formula to each slope:

So, as you can see, there are equal pair of slopes, meaning that they are parallels, which<em> demonstrate that it's actually a quadrilateral figure.</em>
Step-by-step explanation:
I don't exactly know what you're trying to say, but I'm guessing it's an addition question, so...
8 10 15
+2 3 5
10 13 20