Question

Just need help getting this word problem started.
we are going over rational expressions and equations. the question is 30 alligators were captured and tagged by national park officals and then put back in the wild. 1 month later 50 alligators were captured from the same part of the bayou 18 of which had already been tagged. estimate to the nearest whole number how many alligators are in that part of louisiana. if i could just get it started i can do the rest thank you