We spent our maths in grades 4 and 5 doing limitless conversions of this type.
tons, hundredweight, quarters, pounds and ounces.
Pounds shillings and pence
Days, hours, minutes and seconds
And a great many other conversions.
The principles are always the same.
To convert a composite quantity start with the largest item ( hours in this case)
Multiply it by the conversion to the next unit ( 60 to get to minutes )
add the units already at this level
Now repeat for each level.
To convert TO a composite quantity you reverse the process and divide
Start with the smallest quantity.
Divide by its conversion factor.
the remainder are the units to be left at this level
The whole number is now further divided by ever larger units until there is nothing more to do.
so divide 134 minutes by 60 -> 2 with 14 remainder.
ie 2 hours and 14 minutes
The next level is days so try dividing 2 by 24. It doesn't even go once hence there are no days to concern us.
All of this was necessary to pass grade 4 maths in 1960.