Points $A$ and $B$ have the same $y$-coordinate of 13, but different $x$-coordinates. What is the sum of the slope and the $y$-intercept of the line containing both points?
I notice that the line containing both points must be horizontal, since the points have the same $y$-coordinate. That means the slope of the line is 0, and the $y$-intercept is the same as the $y$-coordinate of any point on the line, which is 13. So the sum of the slope and the $y$-intercept is $0 + 13 = 13$. 