answer: an equation is a set of numbers put together within a problem that you are meant to solve in order to receive the final answer.
To use the equation we need a1 and d(the common difference).
We have a1 = 57, we need to find d.
93-84 = 9; 84-75=9; 75-66=9; 66-57=9
d = 9
a350 = 57 + (350-1)(9)
a350 = 57 + (349)(9)
a350 = 57 + 3141
a350 = 3198
Radius of 1 button = r = 3x
Fabric required to cover 1 button = Area of the circle
= 
= 
= 
Total number of buttons = x
Fabric required to cover 1 button =
Fabric required to cover x buttons = 
Hence, fabric required to cover x buttons
sq. units