Answer:
[tex]\huge\boxed{8(2h\ 40min)=21h\ 20min}[/tex]
Step-by-step explanation:
[tex]1h=60min\\\\2h=2(60min)=120min\\\\2h\ 40min=2h+40min=120min+40min=160min\\\\8(2h\ 40min)=8(160min)=1280min\\\\1280:60=\dfrac{1280}{60}=\dfrac{1260}{60}+\dfrac{20}{60}=21+\dfrac{20}{60}\\\\1280min=21h\ 20min[/tex]
[tex]\text{Other method}\\\\8\cdot2h=16h\\8\cdot40min=320min=300min+20min=5h+20min\\\\16h+(5h\ 20min)=21h\ 20min[/tex]
