Compute |1-3+5-7+...+13-15|

8

Step-by-step explanation:

There are a couple different ways you can solve this, but this is generally the quickest way.

Identify a pattern in the problem. We can see that ,  , and so on. Subtracting every two odd numbers (without repeating any numbers) in that problem will always give us the same -2.

So, we see how many pairs of odd numbers there are.

1 and 3,  5 and 7,  9 and 11,  13 and 15. We have four pairs of odd numbers. We can just multiply -2 by 4, which leaves us with an answer of -8.

Finally, since this is also an absolute value equation, the answer will be positive, so the final answer is 8.

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