Answer:
Runner A is running at 9 mph while runner B is running at 4 mph
Explanation:
From online values, 4 laps make 1 mile.
We are told Runner A has made 18 laps in the time it took Runner B to make 8 laps.
This means that runner A has run in mile; 18/4 = 4.5 miles
While runner B has run in miles; 8/4 = 2 miles
Runner A is running 5 mph faster than Runner B, thus speed of runner A is;
V_b + 5 while speed of runner B is V_b.
We know that; time = distance/speed
Thus;
t_a = 4.5/(V_b + 5)
t_b = 2/V_b
Since the times are equal from the question, then;
4.5/(V_b + 5) = 2/V_b
Cross multiply to get;
4.5V_b = 2(V_b + 5)
4.5V_b = 2V_b + 10
4.5V_b - 2V_b = 10
2.5V_b = 10
V_b = 10/2.5
V_b = 4 mph
Since V_a = V_b + 5
Thus, V_a = 4 + 5 = 9 mph
Runner A is running at 9 mph while runner B is running at 4 mph