Chapter 4 - Section 4.5 - Systems of Linear Inequalities - Exercise Set - Page 244: 36b

see graph

Using the intercepts and the testpoint $(0,0)$, the red graph is the graph of $x+y\le8.$ The blue graph (area on and to the left of $x=3$) is the graph of $x\lt3.$ The solution set is the area common to both graphs (darkest shade).