do simultaneous equations
C + L + G = 100 (where C, L and G are the numbers of chewies, lollies and gummies)
and 5C + 4L + 0.25 G= 100 (which i rewrote as 20C +16L+G= 400)
Reduce to get 19C +15L=300
The only multiple of 19 that leaves a balance (from 300) which is a multiple of 15 is 285 (15 x 19= 285). Take it from there