570 + 240 = (570 + 30) + 210 = 600 + 210= 810
360 + 170 = (360 + 40) + 130 = 400 + 130 = 530
760 - 480 = (760 - 400) - 80 = 30 - 80 = 280
510 + 290 = (540 + 60) + 230 = 600 + 230 = 830
320 - 160 = (320 - 100) - 60 = 220 - 60 = 160
430 + 180 = (430 + 170) + 10 = 600 + 10 = 610