Final answer:
Vito could use the equivalent equation 2x - 3(-3x - 4) = -21 to represent the system of equations.
Step-by-step explanation:
The equivalent equation that Vito could use is option C. 2x - 3(-3x - 4) = -21.
To determine the equivalent equation, we need to manipulate the given system of equations in a way that isolates y in terms of x. Let's start with the first equation:
y + 3x = -42
Subtracting 3x from both sides, we get:
y = -3x - 42
Now let's move on to the second equation:
-42x - 3y = -21
Adding 42x to both sides, we get:
-3y = 42x - 21
Dividing both sides by -3, we get:
y = -14x + 7
So the equivalent equation is y = -14x + 7.
To check which option matches this equation, let's simplify each option and compare it to y = -14x + 7. Option C simplifies to 2x - 9x + 12 = -21, which can be further simplified to -7x + 12 = -21. Therefore, the equivalent equation that Vito could use is option C.