Where is the question?
d=vt
d=10(24/60)=4 miles
It is 4 miles to the gift store.
4mi(hr/30mi)(60min/hr)=8 min
It took him 8 minutes on the return trip, for a round-trip time of 32 minutes.
His average speed was (8mi/32min)(60min/hr)=15mph for the whole trip.