Divide 21 by the difference between 18 and 9

Julia is going for a walk through the neighborhood. what unit of measure is most appropriate to describe the distance she walks?

The general form of the quetion of a circle is ax^2+by^2+cx+dy+e=0 where a=b=0 if the circle has a radius of three units and the center lies on the y axis which set of values of a, b, c, d, and e might correspond to the circle

Atemperature of 1.64◦f corresponds to answer in units of ◦c.