(3000+240) : 10 99: 11x (3х3) 812-398x2 (5050-50)х100 669+425: 5 72: (12х6) х 4

(3000=240):10= 324
99:11x(3x3)= 81
812-398x2= 16
(5050-50)x100= 500 000
669+425:5= 218.8 (Вроде 1-4 классы ну ок)
72:(12x6)x4= 4

(3000+240) : 10 = 3000 : 10+240 : 10 = 300+24 = 324
99 : 11×(3×3) = 9×(3×3) = 9×9 = 81
812-398×2 = 812-796 = 16
(5050-50)×100 = 5000×100 = 500000
669+425 : 5 = 669+85 = 754
72 : (12×6)×4 = 72 : 18×4 = 4×4 = 16