Final answer:
The difference in length of the two shelves is 24 cm.
Step-by-step explanation:
The difference in length of the two shelves is obtained by subtracting the length of the smaller shelf from the length of the larger shelf.
In this case, the larger shelf is 89 cm long and the smaller shelf is 65 cm long.
So, the difference in their length is 89 cm - 65 cm = 24 cm.