b. 1.25 hr
step-by-step explanation:
if you have a constant speed of 60 mph, then you have a ratio between 60 mi. to 1 hr. dividing both sides by 60 we get the ratio
1 mi. to
then mult. both sides by 75 we get the ratio
75 mi. to ![\frac{75}{60} hr\\](/tex.php?f=\frac{75}{60} hr\\)
simplifying we get
75 mi. to ![\frac{5}{4} hr](/tex.php?f=\frac{5}{4} hr)
or 1.25 hr.