In a code, "A + B" means A is the mother of B, "A − B" means A is the brother of B and "A × B" means A is the father of B. If P × Q + R, how is P related to R?
Two trains of lengths 150 m and 100 m run on parallel tracks in opposite directions at 54 km/h and 36 km/h respectively. How long will they take to cross each other completely?