Ответ: а) 2390 – 180 : 2 = 2390 - 90 = 2300. б) (1003 – 9) – (506 – 506) = 994 - 0 = 994. в) (700 – 100 + 200) : (701 – 700) = (600 + 200) : 1 = 800 : 1 = 800. г) 300 – 10 : 2 = 300 - 5 = 295.