二年級口算題：尾數(shù)是0三位數(shù)加減法

二年級口算題：尾數(shù)是0三位數(shù)加減法
    （1）310 + 690 =
    （2）830 + 610 =
    （3）930 + 210 =
    （4）440 + 720 =
    （5）290 - 210 =
    （6）590 - 410 =
    （7）270 - 140 =
    （8）650 - 190 =
    （9）840 - 730 =
    （10）340 + 360 =
    （11）920 - 530 =
    （12）580 + 400 =
    （13）540 - 220 =
    （14）350 - 260 =
    （15）550 - 440 =