Chapter 1 - Equations and Inequalities - 1.6 Other Types of Equations and Applications - 1.6 Exercises - Page 147: 37

$1\frac{7}{8}\ hours$

Step 1. Joe will do $1/3$ of the job per hour. Step 2. Sam will do $1/5$ of the job per hour. Step 3. Work together, they will do $1/3+1/5=8/15$ of the job per hour. Step 4. It will take them $15/8=1\frac{7}{8}\ hours$ to do the job.