Feedback: Not quite! Subtract 15 min from 45 min to get 30 min. Since 20 sec is less than 30 sec, borrow 1 min (60 sec), leaving 29 min and 50 sec.
Feedback: Well done! Subtract 15 min from 45 min to get 30 min. Since 20 sec is less than 30 sec, borrow 1 min (60 sec), leaving 29 min and 50 sec.