Introduction to Formulas

Feedback: Not quite! Substitute $x = 3$ into the formula: $y = 2(3) + 3 = 6 + 3 = 9$.

Feedback: Not quite! Substitute $x = 3$ into the formula: $y = 60(3) + 120 = 180 + 120 = 300$. The car will travel 300 miles after 3 hours.

Feedback: Not quite! Substitute $y = 13$ into the formula: $13 = 4x - 7$. Simplify: $20 = 4x$, so $x = \frac{20}{4} = 5$.

Feedback: Not quite! Substitute $y = 4800$ into the formula: $4800 = 500x - 200$. Simplify: $5000 = 500x$, so $x = \frac{5000}{500} = 10$.

Feedback: Not quite! Substitute $y = 200$ into the formula: $200 = 30x + 50$. Simplify: $150 = 30x$, so $x = \frac{150}{30} = 5$.

Feedback: Not quite! For $x \leq 10$, the total cost is given by $y = 50x + 200$. However, since $x > 10$, you apply a 10% discount. The discounted formula becomes: $y = 0.9(50x + 200)$. Substitute $y = 720$: $720 = 0.9(50x + 200)$. Simplify: $720 = 45x + 180$. Solve: $x = \frac{540}{45} = 12$. So, you can print 12 books for $720.