First of all, we know that Emily travels 3/4 of a mile in 4 minutes and 30 seconds (i.e. 9/2 of a minute). So, her current velocity is
of a mile per minute.
At this speed, it takes
minutes to travel 3.42 miles.
Since she left at 8.25, she will arrive at about 8.46, so she's on time for school.