Question

Marta walked 3.9 miles per hour for .72. How far did she walk

Answer 1

Sadly, you neglected to include the unit of the 0.72 .
Here are several possibilities:

0.72 seconds ==> 0.00078 mile
0.72 minutes ==> 0.0468 mile
0.72 hours ==> 2.808 miles
0.72 days ==> 67.392 miles
0.72 weeks ==> 471.74 miles
0.72 fortnights ==> 943.49 miles
0.72 years ==> 24,614.9 miles
0.72 millenia ==> 24,614,928 miles .