there are 60 ( ' ) minutes in 1 degree, and 60 ( " ) seconds in 1 minute.
now, on a Latitude of 42.54°, there are 42° clearly, how much is the 0.54 anyway?
well, we know there are 60 minutes in 1 degree, therefore 0.54 * 60 is how many minutes in 0.54, or 32.4'. So a whole 32' and 0.4 of a minute.
how many seconds in 0.4 minutes? well, there are 60 seconds in 1 minute, thus 0.4* 60, or 24.
L42.54 is then 42° 32' 24".