Chapter R - Section R.3 - Exponents, Roots, and Order of Operations - R.3 Exercises - Page 30: 76

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Using order of operations, the given expression, $ \dfrac{3(-4)+(-5)(-8)}{2^3-2-6} ,$ simplifies to \begin{array}{l}\require{cancel} \dfrac{-12+40}{8-2-6} \\\\= \dfrac{28}{6-6} \\\\= \dfrac{28}{0} \\\\= \text{undefined} .\end{array}