# How can a system of equations be used to predict media use?

##### 1 Answer

Suppose we have collected data about media use, as follows:

Prnt media:

- year 0 (1994)

- year 1 (1995)

- ...

Online media:

- year 0 (1994)

- year 1 (1995)

- ...

We assume a simple, **linear model**, so that we can easily fill in the yearly data and we already have sufficient information to determine the equations.

Let's denote by *the number of years passed since 1994* and by *the average number of hours per person per day spent on media use* .

Our linear equations will have the general form

For **print media use** we have:

and

Therefore, our equation for print media use is

For **online media use** we have:

and

Therefore, our equation for online media use is

Now, we have a system of two linear equations allowing predictions of media use at various data points. (Of course, this is a fictitious example and an oversimplification meant just to illustrate the general idea. We can build a more realistic model by using exponential instead of linear functions).