the first thing you need to calculate is how much less time she plays per day. 3 hours - X = 30 minutesx = 2.5 hours Now that you know how much time has decreased, you need to figure out what percent of the original time the decreased time is. In other words, decreased time = x * 3 hours Plug in the decreased time to get:2.5 hours = x * 3 hoursx = 2.5/3x = 0.83333333333333 = 83.333333% rounds to 83%. Therefore, 30 minutes is a 83% decrease in playing time from the original time of 3 hours.