There are many answers, just make sure that the octagonal envelope is a multiple of 5, which is an integer.

For example, the number of octagonal envelopes is 5,5x0.8 = 4 yuan, and the rest is 16 yuan. One yuan and two houses together, one yuan must be an even number, such as 2, 4, 6, 8, 65, 438+00, 65, 438+02, 65, 438+04. At this time, the numbers of the two-yuan envelope are 7, 6 and 5.

The same is true when there are 10 octagonal envelopes, ***5 boxes.

When there are 15 octagonal envelopes, there are three kinds of five situations.

So there are 7+5+3= 15 kinds of * *.