Working together, sam and charlie can change all the 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 used to solve for the rate, r, for sam to change all the light bulbs in the office building by himself?

We have a work problem here. We can use our knowledge on ratio and proportion in order to set up and equation to determine what is being asked. We do as follows:

1 job / 3 hours for both = 1 job / 8 hours for charlie + 1 / x hours for sam alone

Therefore, the equation would be

1/3 = 1/8 + 1/x

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