6. A graph with a
slope decreases from left to right.

A graph with a slope that decreases from left to right is negative. This slope would mean as x approaches +infinity y would approach -infinity and vice versa. So as x increased y would decrease and as x decreased y would increase. This is called an inverse relationship because the values change in opposite ways.

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