27/2 or 13.5 pieces.
To find the quotient, we need to divide the length of the sub sandwich by the length of each piece she wants to cut it into:
9 ÷ (2/3)
We can simplify this by multiplying the numerator by the reciprocal of the denominator:
9 ÷ (2/3) = 9 × (3/2)
Multiplying straight across:
9 × (3/2) = 27/2
So Jenny will be able to cut the sub sandwich into 27/2 or 13.5 pieces.