Bethany is working at the front desk at Joe's Gym. There were some people lifting weights when she started her shift. Then 5 more people came in and started running on the treadmill and 2 people left. There are now 19 people in the gym. How many people were lifting weights at the start of Bethany's shift? Let's think first. Chain of thought:
We know that 5 people came in and 2 people left after Bethany's shift started, so there was a net change of 5 2 = 3 people. If there are 19 people now in the gym and that is 3 more than when Bethany's shift started, we know there were 19 3 = 16 people lifting weights at the start of her shift.
Therefore, the answer is 16.