The time it took them to ride their bikes is 1hr 42mins.
Time is a fundamental quantity and it is measured in different units like seconds, minutes , hours, days, e.t.c. This units are in converted to one another if needs be.
To calculate the time Maria and her friend spend on riding their bikes , we need to subtract the starting time from finishing time.
This means
2:29 - 12:47
= 1 hr 42mins
Therefore, it will take them 1hrs 44mins