Since posters cost 9 dollars each and picture frames cost 15, it would be multiplication.
The expression would be 9(6)+15(6) or 9x6+15x6.
You have to multiply these numbers. 9 times 6 would be 54. 15 times 6 would be 90.
Now, we need to add these together. 54 plus 90 would be 144.
The total cost for 6 framed posters would be $144.