Final answer:
The other equation that could be paired with the given equation to produce a system of equations with infinitely many solutions is y = 2x + 6.
Step-by-step explanation:
The system of equations given is 2y - 4x = 6 and y = mx + b.
To have infinitely many solutions, the two lines represented by the equations must be coincident (they lie on top of each other).
So, for the given equation, y = 2x + 6 could be the other equation, as it represents the same line. Therefore, the answer is A. y = 2x + 6.