а) (7357+2848)+5152 = 7357+(2848+5152) = 7357 + 8000 = 15357
б) (54271+39999)+10001= 54271+(39999+10001)= 54271+ 50000 = 104271
в)19999+(4801+15200)= (19999+4801)+15200= 24800 + 15200 = 40000
г) 18356+(1644+2135)= (18356+1644)+2135 = 20000+2135=22135