Which has the least value when x=20​

What is the exact area of a circle with a diameter of 50 centimeters? a.87.9 square centimeters b.379.9 square centimeters c.1962.5 square centimeters d.4923.5 square centimeters

Quick translate "x is 12 units from 20" into an equation. what are the values of x being described? if you can answer any of my other questions that'd be great too

Consider the function y = f(x)=3^x the values of f(1/2) and f(1/4). rounded to the nearest hundredth, are__and__ respectively