Final answer:
The cost of another 3 panes of glass is $7.95.
Step-by-step explanation:
To find the cost of another 3 panes of glass, we need to calculate the cost of 1 pane first. Since the nursery owner bought 8 panes for $21.20, we can divide the total cost by the number of panes to find the cost of 1 pane: $21.20 ÷ 8 = $2.65 per pane.
Now that we know the cost of 1 pane, we can find the cost of another 3 panes by multiplying the cost of 1 pane by 3: $2.65 × 3 = $7.95.
Therefore, the cost of another 3 panes of glass is $7.95.