Let the length of the first piece (or the shortest piece) be x cm
Length of the second piece = (x + 3) cm
Also, the length of the third piece = 2x cm. The maximum length of the board available = 91 cm.
...(i)
Also, the third piece is to be at least 5 cm longer than the second.
...(ii)
From (i) and (ii), we have
Hence, the shortest board (or the first board) can have a minimum length of 8 cm and a maximum length of 22 cm.