1770 - 1000 + 770 =
1880 - 1000 + 880 =
1990 - 1000 + 990 =
1800 - 900 + 900 =
1600 - 800 + 800 =
1440 - 700 + 740 =
1260 - 600 + 660 =
1000 - 900 + 100 =
1900 - 950 + 950 =