$$Q = mc\Delta T$$
$$m = \frac{Q}{c\Delta T}$$
$$m = \frac{7600 \text{ Дж}}{380 \frac{\text{Дж}}{\text{кг} \cdot \text{°C}} \cdot 10 \text{ °C}} = \frac{7600}{3800} \text{ кг} = 2 \text{ кг}$$