Given:
Quantity A: \(3x - 4y = -12 \)
Quantity B: \(6x + 2y = 36\)

Take the bottom equation and divide both sides by 2 to get an equivalent equation:
Quantity A: \(3x - 4y = -12 \)
Quantity B: \(3x + y = 18\)

Subtract at the bottom equation from the top equation to get: \(-5y = -30\)
Solve: \(y = 6\)

Find the value of x, take any of the given equations and replace \(y\) with \(6\).
For example, take: \(3x - 4y = -12 \)
Substitute to get: \(3x - 4(6) = -12 \)
Simplify: \(3x - 24 = -12 \)
Add 24 to both sides: \(3x = 12 \)
Solve: x = 4

So, we have:
Quantity A: \(4 \)
Quantity B: \(6\)

Answer: B