1. The points L(4, 0),M(10, 0), and N(7, 5) form Triangle LMN. What is the sum of the slopes of the three sides of the triangle?

Slope between two points P1(x1,y1), P2(x2,y2) is given by:

m=(y2-y1)/(x2-x1)
So the sum of the slopes would be the sum of the slopes LM, MN, and NL.
For LM,
m=(0-0)/(10-4)=0
I am sure you can complete the rest.