To solve the equation you can use the property of the multiplicative inverse, like this
[tex]\begin{gathered} 4.5x=18 \\ \frac{1}{4.5}\cdot4.5x=18\cdot\frac{1}{4.5} \end{gathered}[/tex]Dividing by 4.5 into both sides of the equation is the same as multiplying by the multiplicative inverse of 4.5 on both sides of the equation
[tex]x=\frac{18}{4.5}[/tex]Therefore,
[tex]x=4[/tex]