a) 15243 + 2643 + 27364 - 643 + 4757 - 736= 42000
b) 234 + 13 + 355 + 2345 +266 -513 = (234 +266 ) +(355+2345) +13 - 513 = 500 + 2700 + 13 - 513 = 3200 + 13 - 513 = 2700
c) (56 x 27 + 56 x 35 ) : 62 = [56x (27 + 35)] : 62 = 56 x 62 : 62 =56
K chị nha