Seattle, washington, received rain on 7/10 of the days in a recent month. if this pattern continues, about how many days would it not rain in 90 days

The first step is to find the fraction of the days it would not rain.
3/10
Next we need to understand the there are three days that it will not rain out of 10 days. (that is the pattern) But we need to know how many days it will not rain out of 90 days.
To do this you need to multiply the fraction to get a number over 90 days.
n/90
our work should look like this:
3/10 * 9 = 27/90
Our answer : 27 days there will be no rain

Hope this helps (: