Answer:
Maybe 9.54 cm
Explanation:
1 in. = 2.54 cm
6 in. = 6 × 2.54 cm = 15.24 cm
15.24 cm - 57 = -41.76 cm
He cannot take 57 cm from a 6 inch ruler because 57 cm is more than 6 inches.
Maybe he can take 5.7 cm form a 6 inch ruler.
15.24 cm - 5.7 cm = 9.54 cm