Two nuclear reactors provide 3200 mw of power. if the transmission system loses 5.1% of the energy produced , how much power from these two reactors would customers receive?

If the transmission system loses 5.1% of the energy produced, then you'd say the efficiency of the system is  94.9% ... that's how much of the power goes to the customers.

       94.9% of 3200 MW

    = 0.949 x 3.2 x 10⁹ watts

    =    3,036.8 MW

    =    3.0368 Gigawatts

    =    3,036,800,000 watts

    =    3,036,800  kilowatts