I don't have a massive amount of time to walk you through everything now, so I'll post a few hints:
Look up potential dividers and resistors in parallel.
R2 and R4 form a potential divider.
When the output is low, pin 4 is connected to 0V, via the comparator's output transistor, so R3 is in parallel with R4. Now we have a potential divider with R2 at the top and R3 & R3 in parallel at the bottom.
When the output is high, pin 4 is open circuit. R3 is connected to +V, via R5. V+ is also connected to R2. Now we have a potential divider with R4 at the bottom and R2 in parallel with R3 connected in series with R5.
The output voltage, when the output is high, can be calculated, as R5 and R3 form another potential divider between the non-inverting input and +V.
If R5 has a very low value, compared to R3, say one hundredth of the value, then it can be ignored, thus simplifying the calculations. Here's an application note showing how to calculate the hysteresis for a comparator with a push-pull output, which is similar to R5 being tiny, compared to R3.
http://www.ti.com/lit/ug/tidu020a/tidu020a.pdf?&ts=1589841131589