Alright! To solve this one you first have to find out what 1cm is equal to in km, to do that you have to divide 18km by 3cm:
[18 ÷ 3] = 6.
Now we know that 1cm is 6km. To find how far apart they are on the map you simply divide 54km by 6km:
[54 ÷ 6] = 9.
They are 9cm apart on the map.
