Answer :
Well, since 3/15 can be simplified to 1/5 by dividing the top and the bottom by 3, you would just need to find the decimal of 1/5 which is much more commonly recognized. it's .2 (becasue 1/10 would be .1 and 1/5=2/10 so .1x2=.2)
[tex] \frac{3}{15} = \frac{3*1}{3*5} =^{2/} \frac{1}{5} = \frac{2}{10} =0.2[/tex]