Step-by-step explanation:
length of 1st piece = x inch
length of 2nd piece = 3x inch
length of 3rd piece = 4x inch
x + 3x + 4x = 56
8x = 56
x = 7
Thus,
length of 1st piece = 7 inch
length of 2nd piece = 3 × 7 = 21 inch
length of 3rd piece = 4 × 7 = 28 inch