D. y=20x+18
Explanation:
First, there are 9 posters each costing $2 to post, so 2x9=18
Secondly, it costs $0.20 per flier to print, but we don't have the exact amount of fliers that Rhett printed, instead the equation asks to use x.
Lastly, it would all come together to add up to y(the total amount of money Rhett spent)