To find the equation representing the total charge in dollars (\(y\)) for a delivery of cookies (\(x\)), we will first create a table using the information given about delivery charges.
We can derive some points from the provided information:
-
For 12 cookies:
- Total charge \(y = 20\), therefore the point is \((12, 20)\)
-
For 18 cookies:
- Total charge \(y = 27.50\), therefore the point is \((18, 27.50)\)
-
For 0 cookies (the base case):
- There is a $5 delivery fee regardless of the number of cookies, which gives us the point \((0, 5)\)
Now we can summarize these points in a table format:
| \(x\) (cookies) | \(y\) (total charge) | |--------------------|------------------------| | 0 | 5 | | 12 | 20 | | 18 | 27.50 |
Now, we have three points: \((0, 5)\), \((12, 20)\), and \((18, 27.5)\).
We can find the slope \( m \) between the points \((12, 20)\) and \((18, 27.5)\) to determine the cost per cookie:
\[ m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{27.5 - 20}{18 - 12} = \frac{7.5}{6} = 1.25 \]
This means that the cost per cookie is \(1.25\).
Next, we use the concept of linear equations:
The equation can be represented as:
\[ y = mx + b \]
Where:
- \(m\) is the slope (cost per cookie, which we found to be 1.25)
- \(b\) is the y-intercept (the delivery fee, which is $5)
Plugging in the values:
\[ y = 1.25x + 5 \]
Thus, the equation that represents the total charge in dollars (\(y\)) for a delivery of \(x\) cookies is:
\[ \boxed{y = 1.25x + 5} \]