To determine the maximum number of boxes the truck can carry while crossing the bridge, we need to consider the total weight on the bridge, which includes the weight of the truck and the weight of the boxes.
Let \( x \) be the number of boxes the truck is carrying. The total weight of the truck and the boxes can be represented as:
\[ \text{Total weight} = \text{Weight of truck} + \text{Weight of boxes} \] \[ = 40,000 , \text{pounds} + 40 , \text{pounds/box} \cdot x \]
The bridge can hold a maximum of 75,000 pounds, so we can write the inequality as:
\[ 40,000 + 40x \leq 75,000 \]
This inequality represents the maximum number of boxes \( x \) that the truck can carry to safely cross the bridge.