there were 35 students in a hostel . due to the admission of 7 new students , ; he expenses of the mess were increased by rs . 42 per day while the average expenditure per head diminished by rs 1 . what was the original expenditure of the mess ?
"sol . let the original average expenditure be rs . x . then , 42 ( x - 1 ) - 35 x = 42  7 x = 84  x = 12 . original expenditure = rs . ( 35 x 12 ) = rs . 420 . . answer d"
subtract(multiply(divide(add(42, 42), subtract(42, 35)), 35), add(subtract(subtract(42, divide(add(42, 42), subtract(42, 35))), divide(add(42, 42), subtract(42, 35))), const_2))