I'm having a bit of trouble with this question:
Sue works in a rug shop. She as three rugs with a combined area of $200 m^2$.
She arranged the rugs so they overlap and cover a floor area of $140 m^2$.
The total floor area that is covered by exactly two layers of rugs is $24 m^2$.
What is the floor area that is covered by exactly three layers of rugs, in $m^2$?
The answer I get is $36$, and searching online that's what other people are getting too. However, the given answer is 18. How is that so? Thanks.