You have to multiply the number of flowers by the number that the book gives you, so yellow flowers count x1 (the first digit would be 2, because there are 2), white ones count as x2 and red ones as x4.
The answer is 1728 divided by 6, if you can't solve it yourself, simply calculate that.
This puzzle has given a lot of problems since I published the game, so don't feel bad if you can't solve it. A lot of people got lost in this one.
Hope you're liking the game!