\( (710 + 90) - 400 = 800 - 400 = 400 \)
\( (850 - 600) + 500 = 250 + 500 = 750 \)
\( (12 \times 7) : 7 = 84 : 7 = 12 \)
Ответ: 400, 750, 12.