To find the equation that represents the total charge \( y \) for delivering \( x \) cookies, we can use the information provided about the delivery charges.
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Identify the total charges:
- For 12 cookies: Total charge = $20. Therefore, \( (x_1, y_1) = (12, 20) \).
- For 18 cookies: Total charge = $27.50. Therefore, \( (x_2, y_2) = (18, 27.50) \).
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Calculate the delivery cost excluding the delivery fee:
- The bakery charges a fixed delivery fee of $5, so before considering the delivery fee, the charge for 12 cookies is \( 20 - 5 = 15 \).
- Similarly, the charge for 18 cookies is \( 27.50 - 5 = 22.50 \).
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Determine the cost per cookie:
- For 12 cookies, the cost per cookie is \( 15/12 = 1.25 \).
- For 18 cookies, the cost per cookie is \( 22.50/18 = 1.25 \).
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Setting up the equation:
- From the cost per cookie, we can deduce that the cost of cookies is \( 1.25x \).
- Including the delivery fee, the total charge can be expressed as: \[ y = 1.25x + 5 \]
Thus, the equation that represents the total charge in dollars \( y \) for a delivery of \( x \) cookies is:
\[ \boxed{y = 1.25x + 5} \]