Which of the following equations are equations of circles? choose all that apply.

Timmy uses 1 1 2 cups of sugar for every 2 gallons of lemonade he makes. how many cups of sugar would timmy use if he makes 13 gallons of lemonade?

This is a map of the mars exploration rover opportunity predicted landing site on mars. the scale is 1cm : 9.4km. what are the approximate measures of the actual length and width of the ellipse? i mostly need to know how to set it up : )

Suppose the equation ||x-a|-b|=2008 has 3 distinct real roots and a not =0. find the value of b.