The question states the following: Suppose in Figure P1-22 a ground is connected to the minus side of element 6 and another to the junction of elements 2, 3 and 4. Further, assume that the voltage v4 is 5V and v1 is 10V. What are v2, v3, v5 & v6? I know that voltage is a "through" variable measured in reference to ground (which is 0 V). Does this mean that since v4 is 5V and current is moving towards ground, v6 has to be -5V?