Chapter 1, Equations and Inequalities - 1.7 Solve Absolute Value Equations and Inequalities - 1.7 Exercises - Quiz for Lessons 1.6-1.7 - Page 58: 13

A score of at least $93\%$ is required ($100\%$ is the upper boundary).

Let $x$ be the final exam score. Then our inequality is: $0.8\cdot83+0.2x\geq85\\66.4+0.2x\geq85\\0.2x\geq18.6\\x\geq 93$ Thus a score of at least $93\%$ is required ($100\%$ is the upper boundary).