Step-by-step explanation:
Subtracts those with same units but given that 40" is lower than 50", we need to borrow from 50' which can be read as 50 minutes.
40" is read as 40 seconds. Since 1 minute has 60 seconds, we have:
40" + 60" = 100" and
50' - 1' = 49'
These values will yield 60° 49' 100"
Now that the upper values are higher than the one below, we can now perform the operation:
60° - 30° = 30°
49' - 40' = 9'
100" - 50" = 50"
Checking with a calculator:
