Chapter P - P.2 - Linear Models and Rates of Change - Exercises - Page 17: 43

x = 6

First find the slope using the two given points. To find the slope use the slope definition. m = $\frac{8-3}{6-6} = \frac{5}{0}$ = Undefined Since the slope is undefined the line is a vertical line. It is simply the vertical line x=6.