PLEASE HELP Element X decays radioactively with a half life of 9 minutes. If there are 890 grams of Element X, how long, to the nearest tenth of a minute, would it take the element to decay to 238 grams?

Michael gose to a theme park and rides two different roller coasters that both begin on a raised platform his height while on the first roller coaster measured in feet from the platform height can be modeled by the following graph where t is the number of seconds since the ride began