## Algebra 1: Common Core (15th Edition)

Let p be the pH of the third reading. If the average is between 7.2 and 7.8 inclusive, this is represented by a compound inequality using "and." 7.2≤$\frac{7.4+7.9+p}{3}$≤7.8⟶ multiply each part by 3 7.2×3≤7.4+7.9+p≤7.8×3⟶ multiply 21.6≤15.3+p≤23.4⟶ subtract 15.3 from each part 21.6−15.3≤15.3+p−15.3≤23.4−15.3⟶ subtract 6.3≤p≤8.1