Well first off here we know that one of the figures here is 24 and the other one is 18 so immediatly we can make a fraction out of this by putting the bigger number on the bottom as the denominator and the smaller number on the top as the numerator like so 18/24 we also know that this fraction can easily be simplified like so 3/4 (because 6 goes into each of them evenly) so the scale factor of these 2 figures is 3/4 or C.Enjoy!=)
