He sold 7/8 of pie.
Step-by-step explanation:
A pie cut in thirds = 3 pieces
Each of this 3 pieces is cut into 4 equal pieces, which equals
3 x 4= 12 pieces of cut pie.
Each of this piece is cut into 2 equal slices,
which equals 12 x 2= 24 slices of pie.
If he sold 14 slices, then the fraction sold is
14/24 = 7/8
He sold 7/8 of pie.