Đáp án + Giải thích các bước giải:

c) $\frac{5x}{2.7}$ `+` $\frac{5x}{7.12}$ `+`$\frac{5x}{12.17}$ `+` $\frac{5x}{17.22}$ `=` $\frac{20}{11}$ 

`=>` `5x` `.` `(` $\frac{1}{2.7}$ `+` $\frac{1}{7.12}$ `+` $\frac{1}{12.17}$ `+` $\frac{1}{17.22}$ `)` `=` $\frac{20}{11}$ 

`=>` `5x` `.` `(` $\frac{1}{14}$ `+` $\frac{1}{84}$ `+` $\frac{1}{204}$ `+` $\frac{1}{374}$ `)` `=` $\frac{20}{11}$ 

`=>` `5x` `.` $\frac{1}{11}$ `=` $\frac{20}{11}$ 

`=>` `5x` `=` $\frac{20}{11}$ `:` $\frac{1}{11}$ 

`=>` `5x` `=` `20`

`=>` `x` `=` $\frac{20}{5}$ 

`=>` `x` `=` `4`

  #`HanhDung`  

CHÚC CẬU HỌC TỐT!