Before it charged, the battery was at 23%. In half and hour, it went to 89%. So, it rose 89-23, or 66% in half an hour. Now that we know how much it rose and that there are 30 mins in half an hour, we have to divide 66% by 30 to figure out the answer.
It increases national debt. This happens because the unemployed don't participate in doing taxes because they do not have a job. It also effects other businesses because people with less money won't buy as many things which leads to other companies losing money.