Two-Variable Data: Models and Scatterplots

$100 \times 3^t > 8000 \Rightarrow 3^t > 80$. $3^4=81 > 80$, so $t = 5$ days (since after 4 days = 8100, on day 5 still over). Wait, let me redo: day 1 = 300, day 2 = 900, day 3 = 2700, day 4 = 8100, day 5 = 24300. Exceeds 8000 first at day 4. Actually on day 4: 8100 > 8000 yes. So 4 days. Let me re-examine: After 4 days = $100 \cdot 3^4 = 8100$. So answer is 4 days.