`a):`
`2(1)/5 × 3(4)/9`
`= (2 × 5 + 1)/5 × (3 × 9 + 4)/9`
`= 11/5 × 31/9` `= 341/45`
`b):`
`7(2)/3 : 2(1)/4`
`= (7 × 3 + 2)/3 : (2 × 4 + 1)/4`
`= 23/3 : 9/4`
`= 92/27`
`c):`
`4(2)/3 + 2(3)/4 × 7(3)/11`
`= 4(2)/3 + (2 × 4 + 3)/4 × (7 × 11 + 3)/11`
`= 4(2)/3 + 11/4 × 80/11`
`= 4(2)/3 + 20`
`= (4 × 3 + 2)/3 + 20`
`= 14/3 + 20`
`= 74/3`
Cho mình xin hay nhất nha bạn
@Drew McIntyre