Step-by-step explanation:
1.828 x 10 ^3 is standard for 1828
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
Alejandro is correct because you do not need to add another number to 76.518, as Jiro did, but you need to round it to the nearest tenth.
Glad I could help, and good luck!