To organize and Chair all in a row by row, from the 20 to 1 is a 4 row 2 there are 3 rows 6 a 8 a continuously until 20 rows shall find that all chairs must be used within a .
Want to hold a chair in all achieve 20 row by row, row 1 have 4 2 have 6, row 3 have 8, indefinitely until 20 row. And find out to use the chair all many .