Answer:
At a speed of 57 mph for 8 hr a driver will travel 456 mi
Explanation:
Here we have a summary of the letters for each variable:
Speed ---> r (in units of mph)
Time ---> t (in units of hr)
Distance ---> d (in units of mi)
These three variables are related by the next formula:
d = rt
In the data they give to you: 57 mph and 8 hr, they are telling you the r and the t, respectively:
r = 57 mph
t = 8 hr
The only thing you have to do is replace the values:
d = rt ----> d = 57 mph x 8 hr
d = 456 mi