Answer:
The correct answer is A. The system of equations that represents this situation is x + y = 450 and x - 2y = 18.
Step-by-step explanation:
The correct answer is A. The system of equations that represents this situation is x + y = 450 and x - 2y = 18.
To solve this system of equations, we can use the method of substitution or elimination. Let's use the method of substitution.
From the first equation, x + y = 450, we can solve for x in terms of y by subtracting y from both sides: x = 450 - y.
Now we substitute this value of x into the second equation: (450 - y) - 2y = 18.
Simplifying the equation, we have 450 - y - 2y = 18.
Combining like terms, we get 450 - 3y = 18.
Next, we isolate the variable y by subtracting 450 from both sides: -3y = 18 - 450.
Simplifying further, we have: -3y = -432.
To solve for y, we divide both sides by -3: y = -432 / -3.
Calculating this, we get y = 144.
Now that we know the value of y, we can substitute it back into the first equation to find x: x + 144 = 450.
Subtracting 144 from both sides, we have x = 450 - 144.
Calculating this, we get x = 306.
Therefore, the number of advanced students in the ninth grade is 306.
In conclusion, the correct system of equations is x + y = 450 and x - 2y = 18, and the number of advanced students in the ninth grade is 306.
