Going against the current, a boat takes 7 hours to make a 120 mile trip. when the boat travels with the current on the return trip, it takes 4.5 hours. if x is the speed of the boat is still water and y is the speed of the current, which of the following system of equations could be used to solve the problem?

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.

step-by-step explanation:

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