$400 interest is earned on a principal of $2000 at a simple interest rat 5% interest per year. for how many year was the principal invested

4 Years.

Step-by-step explanation:

Principle ⇒ 2000

Interest ⇒ 400

Rate ⇒ 5%

Time ⇒ _

Simple interest ⇒ p * x * t / 100

⇒ 400 = 2000 * 5 * t / 100

⇒ 400 = 200 * 5 * t / 10

⇒ 400 = 20 * 5 * t

⇒ t = 400 / 20 * 5

⇒ t = 40 / 2 * 5

⇒ t = 20 / 5

⇒ t = 4

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

the answer is (-4,-4)

hope this ! : d