Đáp án:
2 / 1/7 + 8/7 : 8 - 3 : 3/4 . ( - 2 ) mũ 2
= 1/7 + 8/7 . 1/8 - 3 . 4/3 . 4
= 1/7 + 1/7 - 4 . 4
= 2/7 - 16
= 2/7 - 112/ 7
= - 110 /7
3/ 1,4 . 15 /49 - ( 4/5 + 2/3 ) : 2 1/5
= 14/10 . 15/49 - ( 12/15 +10/15 ) : 11/5
= 3/7 - 22/15 . 5/11
= 3/7 - 2/3
= 9/21 - 14/21
= - 5/21
b/ 3 - { 1/6 -x } . 2/3 = 2/3
[ 1/6 -x ] . 2/3 = 3 - 2/3
{ 1/6 - x } . 2/3 = 7/3
{ 1/6 - x } = 7/3 : 2/3
{ 1/6 - x ] = 7/3 . 3/2
1/6 - x = 7/2
x = 1/6 - 7/2
x = - 20 /6
=> Vậy x = - 20/6