__-(15-8)*60=30
__-7*60=30
__-420=30
<u>450</u>-420=30
2/3=40/60
1/2=30/60
3/4=45/60
1/6=10/60
4/15=16/60
7/20=21/60
11/30=22/60
!!!!!!!!!!!!!!!!!!!!!!!