Question

Answer 1

Theo đề, ta có: 

\(\dfrac{31-n}{43-n}=\dfrac{3}{5}\)

\(\Leftrightarrow155-5n=129-3n\)

\(\Leftrightarrow-2n=-26\)

hay n=13

Answer 2

Theo đề bài, ta có:

\(\dfrac{31-n}{43-n}=\dfrac{3}{5}\)

\(\Rightarrow\) 155 - 5n = 129 - 3n

\(\Rightarrow\) -2n = -26

Vậy n = 13

Hok tốt