After a 9% increase in salary, laurie makes $1711.30 per month. how much did she earn per month before the increase?

We know what she is earning now and that it is 9% more than what she used to earn.

The $1711.30 is 109% of what number?   There is your equation in words.

The new salary is all of (100%) plus and extra 9% which = 109%

Now to put it into math:

$1711.30 = 1.09n    (is means =) (of means times and a number next to a variable with no sign between is related by multiplication

$1711.30  =  1.09n
   1.09           1.09       I divided both sides by 1.09   

n = $1570  - her old salary before the increase.  Hope I helped.