Bài 1:
`a. 219 + 453 + 581 + 547`
`= (219 + 581) + (453 + 547)`
`= 800 + 1000 = 1800`
`b. 125 * 51 * 5 * 2 * 8`
`= (125 * 8) * (5 * 2) * 51`
`= 1000 * 10 * 51 = 510 000`
`c. 50 * 15 * 2 * 3 `
`= (50 * 2) * (15 * 3)`
`= 100 * 45 = 4500`
`d. 123 * 18 + 123 * 12 + 123 * 70`
`= 123 * (18 + 12 + 70)`
`= 123 * 100 = 12300`
`e. 98 * 56 + 98 * 44`
`= 98 * (56 + 44)`
`= 98 * 100 = 9800`
`f. 36 * 58 + 36 * 72 + 64 * 67 + 64 * 63`
`= 36 * (58 + 72) + 64 * (67 + 63)`
`= 36 * 130 + 64 * 130`
`= 130 * (36 + 64) = 130 * 100 = 13000`
Bài 2:
`a. 3 * 25 + 15 * 4 - 26 : 2 `
`= 75 + 60 - 13`
`= 122`
`b. 125 * 2 - 100 : 4 + 8 * 5`
`= 250 - 25 + 40`
`= 265`
`c. 49 - 9 + 8 * 25`
`= 49 - 9 + 200`
`= 40 + 200 = 240`
`d. 36 : 6 * 3 - 15`
`= 18 - 15 = 3`
