if 15 students in a class average 75 % on an exam and 10 students average 95 % on the same exam , what is the average in percent for all 25 students ?
"( 15 * 75 + 10 * 95 ) / 25 = 83 % the answer is c ."
divide(add(multiply(15, 75), multiply(10, 95)), 25)