John bought 32 packages with 12 hamburger buns in each package.
32x12=384
384 represents the total amount of hamburger buns John bought.
The question also says 2 full packages and 5 buns were left after the picnic.
Since there are 12 hamburger buns in each package and 2 packages are left, 12x2=24
24 is the total amount is the two packages, but we must add the other 5 that were left over.
This will add up to 29.
Now we take our beginning number of 384 and subtract 29 from it.
This will result in 355 which is our answer!
I hope this helps :)