The slope of line k is

k= 2.5.
To find the slope of a line, let's refer to the slope formula:
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex].
(Check the attched image below).
Point 1: (0, 5)
Point 2: (2, 10)
[tex]m=\frac{5-10}{0-2}=\frac{-5}{-2}=2.5[/tex]
k= 2.5.