Fine the slope of the line on the graph

Take any 2 points through which the line on graph passes,

(0,-1) =(x₁,y₁)

& (2,-4)=(x₂,y₂)

slope=(y₂-y₁)/(x₂-x₁)

=[-4-(-1)]/(2-0)

=-3/2

if you are saying purchasing 3 social media ads and one newspaper ad counts as one purchase then there are:

6 purchases

if you are asking how many of each then:

18 social media ads

6 newspaper ads