the average weight of 20 persons sitting in a boat had some value . a new person added to them whose weight was 50 kg only . due to his arrival , the average weight of all the persons decreased by 5 kg . find the average weight of first 20 persons ?
"20 x + 50 = 21 ( x – 5 ) x = 55 answer : a"
subtract(multiply(add(20, const_1), 5), 50)