1,3*27+1,3*63+2,3*74+2,3*26 1,8*5,7+1,8*4,3

1,3*27+1,3*63+2,3*74+2,3*26=347;
1. 1,3*27=35,1;
2. 1,3*63=81,9;
3. 2,3*74=170,2;
4. 2,3*26=59,8;
5. 35,1+81,9+170,2+59,8=347
1,8*5,7+1,8*4,3 =18;
1. 1,8*5,7=10,26;
2 1,8*4,3=7,74;
3. 10,26+7,74= 18:
347/18≈20