Number of Gift Hampers

[nycmath]

Susan invited 13 of her friends for her birthday party and created return gift hampers comprising one each of 3 dollars, 4 dollars, and 5 dollars gift certificates. One of her friends did not turn up and Susan decided to rework her gift hampers such that each of the 12 friends who turned up got 13 dollars worth gift certificates. How many gift hampers did not contain 5 dollars gift certificates in the new configuration?

[Eigenvalue]

13*(3+4+5)=13*12
(13*12)÷12=13
Divided evenly among 12 friends, each friend would receive $13

[nycmath]

13*(3+4+5)=13*12
(13*12)÷12=13
Divided evenly among 12 friends, each friend would receive $13

On the right track.