Answer:
18 miles
Explanation:
You can start with the equivalence ...
1/2 in = 3 miles
and multiply it by 6.
6·(1/2 in) = 6·(3 miles)
3 in = 18 miles
Towns that are 3 inches apart on the map are 18 miles apart on the ground.
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Why 6? because that is the number 1/2 needs to be multiplied by to get 3. Said another way, ...
3/(1/2) = 3·2 = 6