we know that
To find the average speed divide the total distance by the time
In this problem we have
[tex]total\ distance=15\frac{3}{4}\ miles[/tex]
[tex]time=5\frac{1}{4}\ hours[/tex]
Convert mixed numbers to an improper fractions
[tex]total\ distance=15\frac{3}{4}\ miles=\frac{15*4+3}{4} =\frac{63}{4}\ miles[/tex]
[tex]time=5\frac{1}{4}\ hours=\frac{5*4+1}{4} =\frac{21}{4}\ hours[/tex]
Divide the total distance by the time
[tex]\frac{(63/4)}{(21/4)} =\frac{63}{21} =3\frac{miles}{hours}[/tex]
therefore
the answer is
the average speed is [tex]3\frac{miles}{hours}[/tex]
