Which equation can be used to solve for the rate, r, for Sam to change all the light bulbs in the office building by himself?

Step-by-step explanation:

Given question is incomplete; here is the complete question.

Working together, Sam and Charlie can change all light bulbs in the office building in 3 hours. It would have taken Charlie 8 hours to do the job alone. Which equation can be be used to solve for the rate 'r', for Sam to change all the light bulbs in the office building by himself.

Let Sam can change the bulbs in the office alone in 'r' hours  

Per hour work done by Sam alone =

Let Sam takes he time to change the same bulbs in the office alone = 8 hours

Per hour work done by Sam =

Since, Sam and Charlie complete the work together in time = 3 hours

Therefore, per hour work done by both =

Equation for per work done by both will be,

Per hour work done by both = Per hour  work done by Sam alone + Per hour work done by Charlie

Therefore, equation for the rate 'r' will be,

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