Step-by-step explanation: The scale factor is the larger divided by the smaller. So:
18/8 = 2.25
It is clear that it is more than twice the size of the smaller ( 8 x 2 = 16) so that means that there is still 2 left over. (8/2 = 4, but since that is not the question asked, is more reasonable to say 2/8, which equals .25)
Since the figures are dilated, the side lengths are proportional. The proportion is <em>(side of length in figure 2)/(side of similar figure length in figure 1)</em>.
That is <em>18/8</em>, which simplifies to 9/4, 9 : 4, or 9 to 4.