40 is 20% of 160, so if she saved 40$ and it was 20% off then the original price was 160$!!!
Consider,

. Let's say

then the problem reduces to

. (Do you understand this step?)
So then replacing a again with our definition we get,

.
3.75$ is the price of the item after the 95% price reduction.
Answer:
The overall average is 70 dollars for all weeks together