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