Answer:
If Ava had $28.50 to spend at the farmer's market, and she has $12 left after buying three pumpkins, then the total cost of the three pumpkins must have been:
$28.50 - $12 = $16.50
So Ava spent $16.50 on three pumpkins.
To find the average cost per pumpkin, we can divide the total cost by the number of pumpkins:
$16.50 / 3 = $5.50
Therefore, the average cost per pumpkin was $5.50.