Can someone help me with these 3 problems I have to find the slopes

Answer:
0/5
12/21
-2/5
Step-by-step explanation:
Slope: y2-y1/x2-x1
6. 7-7/20-15=0/5
7. -12-0/-14-7=-12/-21=12/21
8. -2-10/19-(-11)=-12/30=-2/5