Voltage Divider Variation
This one can be solved by inspection. Notice that the 5V source is in series with the 12V source but oriented in the opposite direction. So, the voltage across both resistors is just 7V. You could use the voltage divider equation again to find the voltage from A to B, but since the resistors have the same value the voltage across each of them must also be the same. So the voltage across A and B is 3.5V, with A being the more positive point. Now the voltage between C and A is just the sum of the voltages from C to B and then from B to A.