first u have to find Y2-Y1/X2-X1 , so u will replace the number to the y and x value.
step1: subtract Y2 and Y1. then find the different of x_value, which is 14-10/-7-8
step2: after u find the differences, u will get 4/(-15) .
finally, you will get a slope. y=4/-15x+b.