Answer 1

 

\(\dfrac{60}{x}+\dfrac{60}{x}+10=\dfrac{120}{x}\)

\(\Leftrightarrow\)\(\dfrac{120}{x}+10=\dfrac{120}{x}\)

\(\Rightarrow10=0\) (vô lí)

 

 

Answer 2

\(\dfrac{60}{x}+\dfrac{60}{x}+10=\dfrac{120}{x}\)

\(\Leftrightarrow60+60+10x=120\)

\(\Leftrightarrow10x=120-60-60\)

\(\Leftrightarrow10x=0\)

\(\Leftrightarrow x=0\)

Vậy \(S=\left\{0\right\}\)