To determine how many pieces were not sold, follow these steps:

**Calculate the total number of pieces**: Each pie is cut into eighths, and there are 3 pies.Total pieces=3 pies×8 pieces per pie=24 pieces\text{Total pieces} = 3 \text{ pies} \times 8 \text{ pieces per pie} = 24 \text{ pieces}Total pieces=3 pies×8 pieces per pie=24 pieces**Determine how many pieces were sold**: Three-quarters of all pieces were sold.Pieces sold=34×24=18 pieces\text{Pieces sold} = \frac{3}{4} \times 24 = 18 \text{ pieces}Pieces sold=43×24=18 pieces**Calculate how many pieces were not sold**: Subtract the number of pieces sold from the total number of pieces.Pieces not sold=24−18=6 pieces\text{Pieces not sold} = 24 – 18 = 6 \text{ pieces}Pieces not sold=24−18=6 pieces

Therefore, **6 pieces** were not sold.