Answer:
So he would need 24 days to mow the lawn on his own.
Step-by-step explanation:
The energetic gardener would be able to mow the lawn in twelve days. In eight days he would be able to mow 8/12 of the lawn.
This leaves 4/12 of the lawn left for the lazy gardener to mow. He takes the full eight days to do this so he mows only half as quickly as the energy filled one.
Twice as long as the energetic one.
Hope this helps : )