Assuming that it starts from 2 yuan, the total is ***2*80= 160 yuan, and 240 yuan is missing from 400 yuan, which means that 240 yuan is what we calculated. 15 yuan is 2 yuan. So there are 240/( 15-2) sheets 15 yuan, which cannot be counted. Uncle Wang made a mistake, didn't he, 400 yuan?

15 yuan is the sum of 5 yuan and 10 yuan (because the number is the same).