Can someone please explain the steps of how my professor got these answers?

1. If the forecasted value of the time series variable for period 2 is 22.5 and the actual value observed for period 2 is 25, what is the forecast error in period 2?

Answer: 2.5

2.Suppose for a particular week, the forecasted sales were 4,000. The actual sales were 3,000. What is the value of the mean absolute percentage error?

Answer: 33.3%