Lời giải:

Bài 5.

b) `(-3)/5 * 2/7 + (-3)/5 * 5/7 + 2 3/5`

`= (-3)/5 * ( 2/7 + 5/7) + 2 3/5`

`= (-3)/5 * 1 + 2 3/5`

`= (-3)/5 + 2 3/5`

`= 2`.

c) `75% - 1 1/2 + 0,5 : 5/12 - (-1/2)^2`

`= 75/100 - 3/2 + 1/2 * 12/5 - (-1/4)`

`= (-3)/4 + 6/5 + 1/4`

`= ( (-3)/4 + 1/4) +6/5`

`= (-2)/4 + 6/5`

`= 1/5`.

d) `(-11)/12 * 18/25 + (-11)/12 *7/25 + 11/12`

`= (-11)/12 *(18/25 + 7/25) + 11/12`

`= (-11)/12 * 1 + 11/12`

`= (-11)/12 + 11/12`

`= 0`.

e) `3/8 - 4/5 - (-12)/40`

`= 15/40 - 32/40 + 12/40`

`= 15/40 + ( (-32)/40 + 12/40)`

`= 15/40 + (-20)/40`

`= (-1)/8`

f) `-3,5 + 4,6 + 3,5 + (-1,6)`

`= (3,5 - 3,5) + (4,6 - 1,6)`

`= 0 + 3`

`= 3`.

g) `5/11 * 18/29 + (-5)/11 * 8/29 + 5/11 * 19/29`

`= 5/11 * 18/29 + 5/11 * (-8)/29 + 5/11 * 19/29`

`= 5/11 * (18/29 - 8/29 + 19/29)`

`= 5/11 * 1`

`= 5/11`.

h) `25% - 2 2/13 - ( - 1/2)^2 + 0,25 : 1/12`

`= 1/4 - 28/13 - 1/4 + 1/4 * 12`

`= (1/4 -1/4) + 1/4 * 12 - 28/13`

`= 0 + 3 - 28/13`

`= 39/13 - 28/13`

`= 11/13`.

i) `(2,7 - 51,4) - (48,6 - 7,3)`

`= 2,7 - 51,4 - 48,6 + 7,3`

`= (2,7 + 7,3) + (-51,4 - 48,6)`

`= 10 + (-100)`

`= -90`.

k) `4/11 * (-2)/7 + (-4)/11 * 4/7 + 4/11 * (-1)/7`

`= 4/11 * (-2)/7 + 4/11 * (-4)/7 + 4/11 * (-1)/7`

`= 4/11 * ( (-2)/7 + (-4)/7 + (-1)/7 )`

`= 4/11 * (-1)`

`= (-4)/11`

l) `2/(-9) * 7/15 + (-2)/9 * 8/15 + 2 2/3`

`= (-2)/9 * 7/15 + (-2)/9 *8/15 + 2 2/3`

`= (-2)/9 * (7/15 + 8/15) + 2 2/3`

`= (-2)/9 * 1 + 2 2/3`

`= (-2)/9 + 2 2/3`

`= (-2)/9 + 24/9`

`= 22/9`.

m) `(12/61 - 31/22 + 14/91) * (1/2 - 1/3 -1/6)`

`= (12/61 - 31/22 +14/91) * (3/6 - 2/6 - 1/6)`

`= (12/61 - 31/22 + 14/91) * 0`

`= 0`.

n) `(-5)/7 + 8/11 + ( (-2)/7 ) + 1/2 + 3/11`

`= ( (-5)/7 + (-2)/7 ) + ( 8/11 + 3/11) + 1/2`

`= -1 + 1 + 1/2`

`= 0 + 1/2`

`= 1/2`.

o) `11/17 - 8/19 + ( (-3)/4 ) + 6/17 - 30/19`

`= (11/17 + 6/17) + ( -8/19 - 30/19) + (-3)/4`

`= 1 + (-2) + (-3/4)`

`= -1 + (-3/4)`

`= (-7)/4`.

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