Question 178339
10u/9t divided by 14u/15tu 

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Invert the denominator and multiply:

[10u/9t] * [15tu/14u]

Cancel factors common to a numerator and a denominator
such as 2,3,t,u.

= [5u/3] * [5/7]

= 25u/21
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Cheers,
Stan H.