4. Viết số thích hợp vào chỗ chấm. a) 129times ldots ldots =3times 129 b) 3times 25=(ldots ldots .+20)times 3 c) (12times 7)times 20=12times (ldots ldots times 20) d) 16times 4times 2=2times ldots ldots =8times ldots ldots

a) b) c) d)