Hello, thank you for taking the time to post your question!
For slope you want to use the formula
m = (y2 – y1) / (x2 – x1)
for this set of values that would be
m = (14 – 10) / (-7 – 8) = 4 / -15
so the slope between this set of points would be -4/15!
I hope that helps get you moving in the right direction! Feel free to reach out if you have any additional questions beyond that :)