Voltage at comparator entrances
For this question, all you need to know is that opamp inputs don't draw current. This turns it into a straightforward resistor divider. 







simulate this circuit &ndash; Schematic created using CircuitLab

You can calculate it in a few different ways, but the way it probably wants you to do it is using current. 

In the case where V2 = 0:


What is the total current through the resistors?
Knowing the total current, you can calculate the voltage drop across R1
Then you just add this voltage drop to V1 to get V+


The same thing happens for V2 = 5V