Final answer:
Ella sold 14 dozen cookies.
Step-by-step explanation:
To find the number of dozens of cookies Ella sold, we need to calculate the profit she made from selling the cookies. We know that Ella's profit is $66 and she pays $10 for ingredients. So, her profit after deducting the cost of the ingredients is $66 - $10 = $56.
Ella sells each dozen of cookies for $4, which means she makes $4 profit for every dozen sold. To calculate the number of dozens of cookies she sold, we divide her total profit by the profit per dozen: $56/$4 = 14.
Therefore, Ella sold 14 dozen cookies.