Anuclear reaction releases 9.00 × 10^13 j of energy. what was the change in mass?
5.0 × 10^-4 kg
1.0 × 10^-3 kg
5.0 × 10^-3 kg
5.0 × 10^-2 kg

A nuclear reaction is the perfect place to use   E = mc² .

                                              9.00 x 10¹³ = (m) (3 x 10⁸)²

Divide each side by  (3 x 10⁸)² :      m =  (9 x 10¹³) / (3 x 10⁸)²

                                                       m = (9 x 10¹³) / (9 x 10¹⁶) = 0.001 kg

Now, take several steps back, and look at what you've been working with:
You just showed that 1 gram of matter, when completely converted to energy,
produces the energy for a 100-watt light bulb to run for  28,519 years !