The proportion between the first measures is:
[tex]\frac{45}{27}[/tex]Now, if we want to maintain the same proportion we need that the second map fullfils:
[tex]\frac{12}{x}[/tex]Equating this proportions and solving for x we have:
[tex]\begin{gathered} \frac{45}{27}=\frac{12}{x} \\ x=\frac{12}{\frac{45}{27}} \\ x=\frac{36}{5} \\ x=7.2 \end{gathered}[/tex]Therefore the width would be 7.2 cm