You simply have to multiply the number per flower type to its respective number of pieces bought. But first, let's find the price for each piece. Since the price given is per half dozen, the price for each piece would be:
Rose: 5.29/6 = $0.882
Carnation: 3.59/6 = $0.598
Tulip: 4.79/6 = $0.798
Total amt = 4($0.882) + 6($0.598) + 9($0.798) = $14.3
Since the estimated amount if close to the total amount, therefore, I agree.