Final answer:
The equation for finding Chris's wage for a given number of hours is w = 7.5h, as her wages vary directly with the number of hours worked. We calculate the constant rate of change (k) using the provided information, resulting in k = 7.5, the wage per hour.
Step-by-step explanation:
Chris's wage varies directly with the number of hours she works, meaning there is a constant rate of change in her wage with respect to the hours worked. This type of relationship is described by a linear equation of the form w = kh, where w represents the wage, h represents the hours worked, and k is the constant rate of change, or the wage per hour.
To find the value of k, we use the information provided: for 20 hours, Chris earns $150. The equation would be 150 = 20k. Solving for k, we get k = 150 / 20 = 7.5. Therefore, the equation for finding Chris's wage w for a given number of hours h is w = 7.5h, which corresponds to option A.