Problem 27. Two resistors, A and B, are connected in series to a 12 V battery. A voltmeter connected across resistor A measures a potential difference of 6.7 V. When the two resistors are connected in parallel across the 12 V battery, the current in B is found to be 1.6 A. Find the resistance of A. On problem 28 how does it get solve? I'm stumped.