You were able to send 30 snapchat stories in 9 minutes. At this rate, how many snapchat stories can

You were able to send 30 snapchat stories in 9 minutes. At this rate, how many snapchat stories can you send in 21 minutes?

Set up a proportion of stories to minutes where s is the number of Snapchat stories you can send in 21 minutes:
30/9 = s/21

To solve this proportion for s, we type it in our math engine and we get:
s = 70