Answer:
c=71/23
Step-by-step explanation:
I think
Answer:12300
Step-by-step explanation:12.3x1000
The letter "x" is often used in algebra to mean a value that is not yet known. It is called a "variable" or sometimes an "unknown". In x + 2 = 7, x is a variable, but we can work out its value if we try! so im pretty sure its 20
The ratio A/r² would represent

which is the circumference of a circle divided by its diameter.
You can see this because the area of a circle is

r² and if you divided that by the radius squared, you are given pi which is the circumference of a circle divided by its diameter.