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This problem trains for: SAT-I, SAT-II, AMC-8, AMC-10, Math Kangaroo 5-6, Math Kangaroo 7-8.

If the following is a proportion:

equation

Evaluate the expression:

equation

Given the proportion:

equation

The product of the means (inner terms) is equal to the product of the extremes (outer terms):

equation

We can substitute this value for ab in the expression:

equation

Instead of blindly executing operations, we can apply clever transformations:

equation