3 times a number increased by 1 is between -8 and 13. Let's take this algebraic expression in 4 parts: Part 1 - The phrase a number means an arbitrary variable, let's call it x: x Part 2 - 3 times this number means we multiply x by 3: 3x Part 3 - Increased by 1 means we add 1 to 3x: 3x + 1 The phrase between means we have an inequality: -8 <= 3x + 1 <=13