Final answer:
The cost of 5 burgers and 7 fries from Evan's food truck is calculated by substituting the values into the provided expression 0.25b² + 0.5f, which results in a total cost of 9.75 dollars.
Step-by-step explanation:
The student provided an expression 0.25b² + 0.5f that represents the cost of b burgers and f fries from Evan's food truck. To calculate the cost of 5 burgers and 7 fries, we need to substitute b with 5 and f with 7 in the given expression.
So the cost C will be C = 0.25(5)² + 0.5(7).
Calculating the square of 5 we get 25; thus, the cost for burgers is 0.25 * 25 = 6.25 dollars. The cost for fries is straightforward: 0.5 * 7 = 3.5 dollars. Adding these two amounts gives us C = 6.25 + 3.5 = 9.75 dollars.
Therefore, the total cost of 5 burgers and 7 fries from Evan's food truck is 9.75 dollars.