$35.99 includes 250 'free' minutes. anything over that is $0.2 per minute. So if she used 440 total minutes that means 440 minus 250 free minutes = 190 minutes over. 190 minutes times $0.2/minute = $38 extra
say, you have half a pie, and 2 sisters, if you divide the half-pie in 3 equal pieces, how much is everyone getting of the whole pie? well, is the quotient of 1/2 and 3.