We need to determine which ordered pairs $(x, y)$ are solutions to the equation $3x - 4y = 21$. This can be done by substituting each pair of values into the equation and checking if the equation holds true.

1. For $(-1, -6)$: $3(-1) - 4(-6) = -3 + 24 = 21$ This is true, so $(-1, -6)$ is a solution.

2. For $(-3, 3)$: $3(-3) - 4(3) = -9 - 12 = -21$ This is false, so $(-3, 3)$ is not a solution.

3. For $(11, 3)$: $3(11) - 4(3) = 33 - 12 = 21$ This is true, so $(11, 3)$ is a solution.

4. For $(7, 0)$: $3(7) - 4(0) = 21 - 0 = 21$ This is true, so $(7, 0)$ is a solution.

Correct solutions:

$(-1, -6)$, $(11, 3)$, and $(7, 0)$.

Would you like more details or have any further questions?

Here are some related questions:

1. What is the general process for solving linear equations in two variables?
2. How can you determine the slope and intercept of the line $3x - 4y = 21$?
3. What does the graph of the equation $3x - 4y = 21$ look like?
4. How can you verify if a point is a solution to a linear system of equations?
5. How do you solve systems of equations using substitution or elimination methods?

Tip: Always double-check by substituting values back into the equation to verify the solution.