Answer:
Proportion states that the two equal ratios or fractions are equal.
Use conversion:
1 m = 100 cm
As per the statement:
The actual width ( w) of a regulation soccer field is 90 meters (m), and the actual length is 120 meters (m
⇒Actual length = 120 m and Actual width = 90 m
It is also given that:
A coach has drawn a scale model of the field on a blackboard. If the longest side of his drawing is 18 cm.
⇒ Drawing length = 18 cm = 0.18 m
By definition of proportion:

Substitute the given values we have;

By cross multiply we have;

Simplify:

Divide both sides by 120 we get;
m
Or
cm
Therefore, the other side of the drawing width is 13.5 cm