Question 281060
Is this  a trick question? The problem states that you walked 9'31" so that is how far you walked!
FYI 
9'31" normally means 9 feet 31 inches.
It can mean 9 minutes and 31 seconds when referring to angles and arcs but not when dealing with time.
APPENDIX VII Recommended Unit Symbols, SI Prefixes, and Abbreviations

ewh.ieee.org/soc/ias/pub-dept/abbreviation.pdf

converting 9 minutes 31 sec into  hour involves
9 minutes 31/60 seconds
540/60 +31/60=571/60 = minutes
571/60=9.5166 minutes
9.5166/60=hours
.15861111 hours
.158611*3.5 =.55513888 miles