for the past n days , the average ( arithmetic mean ) daily production at a company was 30 units . if today ' s production of 90 units raises the average to 35 units per day , what is the value of n ?
"( average production for n days ) * n = ( total production for n days ) - - > 30 n = ( total production for n days ) ; ( total production for n days ) + 90 = ( average production for n + 1 days ) * ( n + 1 ) - - > 30 n + 90 = 35 * ( n + 1 ) - - > n = 3 . answer : e ."
subtract(divide(subtract(90, 30), subtract(35, 30)), const_1)