Hi,

Let x represent gallons need to drive 374mi



cross multiply to solve

204x = 9*274

x = 9*274/204



John can rinse them in 135 minutes by himself. 

Bob takes 90 minutes to rinse these dishes

Let x represent the time it takes together.  Per minute being the Equalizer

1/135 + 1/90 = 1/x  

Mulitplying each term by 90*135*x so as all denominators = 1

90x + 135x = 90*135

225x = 90*135

x = 90*135/225 = 54 minutes together 

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