What is the radius of the circle whose equation is x^2+y^2=9

The graph represents the gallons of water in a water tank with respect to the number of hours since it was completely filled

Tom is the deli manager at a grocery store. he needs to schedule employee to staff the deli department for no more that 260 person-hours per week. tom has one part-time employee who works 20 person-hours per week. each full-time employee works 40 person-hours per week. write and inequality to determine n, the number of full-time employees tom may schedule, so that his employees work on more than 260 person-hours per week. graph the solution set to this inequality.

Typically a point in a three dimensional cartesian coordinate system is represented by which of the following answers in the picture !