Average speed = distance / time
From the question;
distance = 2 1/8 miles = 17/8 miles
time = 1/2
substitute the values into the formula;
[tex]\text{Average sp}eed\text{ =}\frac{\frac{17}{8}}{\frac{1}{2}}[/tex][tex]=\frac{17}{8}\times\frac{2}{1}[/tex][tex]=\frac{17}{4}[/tex][tex]=4\frac{1}{4}\text{ miles per hour}[/tex]