Question

A magazine has 120 pages. There are 28 full-page ads and 12 half-page ads. The rest of the magazine consists of articles.

Answer 1

For this case we propose the following variables:

x: Let the variable that represents the full-page ads

y: Let the variable that represents the half-page ads

a: Let the variable that represents the number of articles

If the magazine consists of 120 pages in total we have:

$x + y + a = 120$

According to the statement we have:

$x = 28\\y = 12$

We clear the value of the variable a:

$a = 120-x-y\\a = 120-28-12\\a = 80$

Thus, 80 pages of the magazine are articles.

Answer:

$a = 120-x-y\\a = 80$