Ryan mows lawns in the summer. He charges $15 for every 12 hour of mowing. This is represented by the equation y=15x , where y is the total amount Ryan charges and x is the number of 12 -hour sessions of mowing. If Mr. Smith’s lawn takes 2 hours to mow and Mrs. Jones's lawn takes 3.5 hours to mow, how much more would Ryan charge Mrs. Jones than Mr. Smith?
$
.