You need to find the cost of one marker. You just simply have to divide the money by the number of markers.
[tex]6 \div 20 = m[/tex]
[tex]m = 0.3[/tex]
Now to actually make it apply to the problem, you have to make sure there is a zero in the hundredths place.
So it will look like this:
[tex]m=0.30$[/tex]
