Đáp án:
`a, 400`
`b,0`
`c,-488`
Giải thích các bước giải:
`a,`
`47 × 8 - 27 × 9 + 47 × 12 - 27 × 11`
`= [47 × 8 + 47 × 12] - [27 × 9+ 27×11]`
`= [47 × (8+12)] - [27 × (9+11)]`
`= 47 × 20 - 27 × 20`
`= 20 × (47-27)`
`= 20 × 20`
`= 400`
`b,`
`24 × 42 - 35 × 24 - 24 × 7`
`= 24 × (42 - 35 - 7)`
`= 24 × 0`
`= 0`
`c,`
`42 × 13 - 22 ×5 - 42 × 22`
`= 42 × 13 - 42 × 22 - 22×5`
`= 42 × (13-22) - 22×5`
`= 42 × (-9) - 22×5`
`= -378 - 110`
`= -488`