Question

When u solve an equation you must do the same thing to both sides of the equal sign

Answer 1

According to the properties of equality,

$\begin{gathered} a=b \\ \Rightarrow a\cdot c=b\cdot c \end{gathered}$

In our case,

$\begin{gathered} \frac{x}{3}=5 \\ \Rightarrow3\cdot\frac{x}{3}=3\cdot5 \\ \Rightarrow3\cdot\frac{x}{3}=5\cdot3 \end{gathered}$

Therefore, the missing number is 3.