Let the initial number of flowers that Willie set out with be x.
When he sneezed, he knocked off the petals of 2/3 of x and he threw away the petal-less ones. So the remaining number of flowers with him now is x-2/3x = 1/3x
He then added 4 more to the remaining. So the number of flowers with him now is 1/3x + 4 = (x+12)/3
On his way, he dropped 4/5th of what he had into a mud puddle. Which is 4/5((x+12)/3)
= (4x + 48)/15
The number of flowers left with him will be
(x+12)/3 - (4x+48)/15 = (x + 12)/15
He then picked up 3 flowers from Suzabelle's mother's garden. The number of flowers he now has
= (x + 12)/15 + 3
Suzabelle said she will now have a dozen (12) flowers, before she only had 5. So now she got 12-5=7 flowers from Willie.
Which implies :
(x + 12)/15 + 3 = 7
On solving for x, we get x = 48.
Thus, Willie set out with 48 flowers the first time.