To solve this question, first we need to find out the price of a single donut.
12 donuts = $ 6.00
1 donuts = $6.00 / 12
1 donuts = $ 0.50
After that, we just need to multiply the price for a single donut with the required amount (9), which will be:
9 x $ 0.50 = $ 4.50 . . . . for 9 donuts