The initial balance was 18 and 9b, so we can write an equation and find the value of b:
[tex]\begin{gathered} 18=9b \\ b=\frac{18}{9} \\ b=2 \end{gathered}[/tex]
So if the value of b is 2, let's calculate the missing value in order to rebalance the equation:
[tex]\begin{gathered} 18\colon x=3b \\ \frac{18}{x}=3\cdot2 \\ \frac{18}{x}=6 \\ 6x=18 \\ x=\frac{18}{6} \\ x=3 \end{gathered}[/tex]
So the number to divide on the left is 3.
