Question

х + 580 = 800 + 900
450 + х = 1200 - 400

Answer 1

580+800=1380

580+900=1480




450+1200-400

1200-400=800

800+450=1250

Answer 2

$x + 580 = 800 + 900 \ x + 580 = 170000 \ x = 170000 - 580 \ x = 169420 \ \ 450 + x = 1200 - 400 \ 450 + x = 800 \ x = 800 - 450 \ x = 350$