Answer:
C. $40.50
Explanation:
OK so, If 20 articles cost ? 90, then the cost of 9 articles is ?
First you need to find out how much is 1 article.. Divide 90 by 20 you get, $4.5. now multiply 4.5 by 9. Which you get... 40.5. In other words it can also be written as, 40.50.
Hope its correct ;w;