You are getting confused I think between the Point of Safe Return (PSR) and Point of Equal Time (PET) formula.

Time to the PSR = (E x H)/(O + H) where E = safe endurance

Distance to the PET = (D x H)/(O + H) where D = Sector distance

For this PSR question, use the PSR formula to find the "TIME TO PSR", then use the DISTANCE/SPEED/TIME rule to find the distance to the PSR.
(DISTANCE = SPEED x TIME)