Answer:
He forgot to flip the second fraction.
Explanation:
He has:
−8/9 ÷ 9/8 = −8/9 × 9/8 = −72/72 = −1
He made a mistake. When you change a division to a multiplication, you must use the reciprocal of the second fraction. You have to flipt the second fraction. He did not flip it.
This is correct:
−8/9 ÷ 9/8 = −8/9 × 8/9 = −64/81