Part A.
We know there are 12 months in a year, then we have the following rule of three:
weere x denotes the corresponding years for 72 months and is given by
that is,
Therefore, 72 months is equal to 6 years.
Part B.
In this case, we know there are 365 days in 1 year then our rule of three is
this means that in 72 months (6 years) there are 2190 days.
Part C.
We know there are 24 hours in 1 day, so our rule of three is
Hence, 72 months are equal to 52560 hours