Answer:
6u/(13v)
Explanation:
Any of ...
6u to 13v
6u : 13v
6u/(13v)
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A ratio can be expressed in any of the forms shown above. We probably prefer a symbol, (:) or (/), instead of a word (to) as the ratio indicator. The wording, "the ratio of A and B" would usually be interpreted at A/B, rather than B/A. The latter interpretation might be used in some contexts where it is clear that the order in the English phrase is intentionally (or inadvertently) reversed.