Diana, Yen and Zara each sold an equal number of cupcakes. Diana collected a total of $71.70 from selling 6 chocolate cupcakes and some matcha cupcakes. Yen collected a total of $74.40 from selling 9 chocolate cupcakes and some matcha cupcakes. How much did Zara collect if she sold only matcha cupcakes?
Yen collected more money than Diana from the sale of the cupcakes but the number of cupcakes sold by each girl was the same. This shows that each chocolate muffin is higher priced than each matcha muffin. 

Amount that Yen collected more than Diana
= 74.40 - 71.70
= $2.70

Number of more chocolate cupcakes that Yen sold
= 9 - 6
= 3

Extra amount collected from the sale of each chocolate muffin
= 2.70 ÷ 3
= $0.90

Total extra amount collected from the sale of 6 chocolate cupcakes
= 6 x 0.90
= $5.40

If Diana sold only matcha cupcakes, she would collect $5.40 less than her original amount.

Amount that Zara collected if she sold only matcha cupcakes
= 71.70 - 5.40
= $66.30

Answer(s): $66.30