AMC 8 L1: Calculation Tricks

Complete problem set with solutions and individual problem pages

Problem 15 Easy

Suppose that a\otimes b=ab-a-b. If (3\otimes x)\otimes3=11, then x=            .

Answer:5
Solution

Suppose 3\otimes x=y, then y\otimes3=11\Rightarrow 3y-y-3=11\Rightarrow y=7.

3\otimes x=7\Rightarrow 3x-3-x=7\Rightarrow x=5.

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