# How do you find the slope given x=7?

slope of a straight line is the tangent of the angle subtended by it with the positive direction of x-axis. Here the line $x = 7$is parallel to y-axis , so it subtends angle $\frac{\pi}{2}$ with the x-axis . Hence slope is $\tan \left(\frac{\pi}{2}\right)$ i.e. undefined.