Đáp án:
Giải thích các bước giải:
a, x+30%.x=-1,31
x.( 1+30%)=-1,31
x.`13/10`=-1,31
x = -1,31 : `13/10`
x =`-131/130`
b, (x-`1/2` ) : `1/3`+`5/7`=9`5/7`
(x-`1/2` ) : `1/3` =9`5/7`-`5/7`
(x-`1/2` ) : `1/3` =9
x-`1/2` =9 x `1/3`
x-`1/2` =3
x = 3 +`1/2`
x =`7/2`
c, `1/2`x - `3/4`=`14/9` . 3/7`
`1/2`x - `3/4`=`2/3`
`1/2`x = `2/3`+`3/4`
`1/2`x =`17/12`
x = `17/12` : `1/2`
x = `17/6`
