Final answer:
By solving the system of equations representing the number of child and adult tickets sold at the county fair, we find that the number of adult tickets sold is 300.
Step-by-step explanation:
To determine how many adult tickets were sold on Tuesday at the county fair, we use the given system of equations representing the number of child tickets (x) and adult tickets (y):
- The total number of tickets sold is 525, which gives us the equation x + y = 525.
- The total revenue from ticket sales is $2775. Since tickets cost $7 for adults and $3 for children, we have the revenue equation 7y + 3x = 2775.
By solving the system of equations, we can find the value for y, the number of adult tickets. Subtracting 3x from both sides of the second equation, we get 7y = 2775 - 3x. Knowing from the first equation that x = 525 - y, we can substitute (525 - y) in place of x to get 7y = 2775 - 3(525 - y).
Simplifying the equation, we have:
7y = 2775 - 1575 + 3y
7y - 3y = 1200
4y = 1200
y = 1200 / 4
y = 300
Therefore, the number of adult tickets sold on Tuesday is 300, which is option D.