# Is this simple ratio and proportion?

For the given circuit above, resistors $$X$$ and $$Y$$ have fixed values, and the range of resistance of the variable resistor is 0 to 1000 ohms. If the variable resistor is set at $$0\:\Omega$$, $$V_A = 27\: V$$, and $$V_A = 52\: V$$ when it is set to $$1000 \:\Omega$$. Determine at what resistance (in ohms) must the variable resistor be set such that the output voltage measured between $$A$$ and ground is $$42 \: V$$.

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