二年级口算题:整十数减两位数的减法 (1)80 + 51 = (2)60 + 21 = (3)60 + 36 = (4)60 + 21 = (5)90 + 71 = (6)50 + 49 = (7)60 + 50 = (8)80 + 61 = (9)80 + 34 = (10)80 + 75 = (11)50 + 19 = (12)50 + 27 = (13)20 + 11 = (14)60 + 14 = (15)80 + 22 =