If Rita has driven 30 miles so far (three-fifths of the way home), you can calculate what is the total length of her drive using the following steps:
x ... total length
three-fifths of the way home = 30 miles
3/5 of x = 30 miles
3/5 * x = 30 /*5/3
x = 30 * 5/3
x = 50 miles
The total length of her drive is 50 miles.