1. **State the problem:** Avery has $30 to spend on cheeseburgers and seltzer. The budget constraint shows all combinations of cheeseburgers and seltzer he can buy. 2. **Identify prices from the diagram:** The budget constraint intercepts are 20 cheeseburgers (when 0 seltzer) and 30 cans of seltzer (when 0 cheeseburgers). 3. **Calculate prices:** - Price of cheeseburgers $p_c = \frac{30}{20} = 1.5$ per cheeseburger. - Price of seltzer $p_s = \frac{30}{30} = 1$ per can. 4. **Budget constraint formula:** $$p_c \times C + p_s \times S = 30$$ where $C$ is cheeseburgers and $S$ is seltzer. 5. **Effect of seltzer price increase:** If $p_s$ increases, the maximum cans of seltzer Avery can buy decreases because $\frac{30}{p_s}$ is smaller. 6. **Adjusting the budget line:** - The cheeseburger intercept remains at 20 (since $p_c$ and income unchanged). - The seltzer intercept moves left to $\frac{30}{p_s^{new}}$ cans. 7. **Summary:** The budget line pivots inward on the seltzer axis, showing fewer cans can be bought for the same income. **Final answer:** If the price of seltzer increases, the budget constraint rotates inward from the seltzer intercept, reducing the maximum seltzer cans purchasable, while the cheeseburger intercept remains at 20.