Đáp án:
`a) (4-7/12):2+7/12`
`=41/12.(1/2)+7/12`
`=41/24+7/12`
`=55/24`
`b) 4.(1/2)^3+1/2`
`=1/2[4.(1/2)^2+1]`
`=1/2.(4.1/4+1)`
`=1/2.(1+1)`
`=1/2.2=1`
`c) 5/21(4 1/5.(7 3/4)+5 1/4. 4,2)`
`=5/21.(21/5.(31/4)+21/4.(21/5))`
`=5/21.(21/5)(31/4+21/4)`
`=(31+21)/4=52/4=13`