Question

Can someone explain to me step-by-step

Answer 1

You can use any two clear points from the graph to get the slope, like (0,4) and (-2,0)

then you can use this rule to find the slope :
(y2-y1)/(x2-x1)
=(0-4)/(-2-0)
= -4/-2
=2

so the slope is 2

hope this helps !