figure a,c, and d are all polygons.
a polygon is a closed figure with a finite number of straight sides and angles. since figure b has rounded sides and only one angle, it does not classify as a polygon.
hope this : )
you make 23 a day plus 3.60 per sale
income = 23+ 3.6 s
you want to make at least 84
84 ≤ 23+ 3.6 s
subtract 23 from each side
84 -23 ≤ 23-23 +3.6s
61 ≤ 3.6s
divide by 3.6 on each side
61/3.6 ≤ 3.6s/3.6
16.94444 ≤ s
you must make more than 16.94444 sales
but you cannot make part of a sale so
you must make at least 17 sales