To calculate the slope of any line, you need to know at least two points of said line.
The formula for the slope is
[tex]m=\frac{y_1-y_2}{x_1-x_2}[/tex]Where
(x₁,y₁) are the coordinates of one point of the line
(x₂,y₂) are the coordinates of a second point of the line
For line "a" the known points are (2,-15) and (5,10)
The slope of this line is
[tex]m_a=\frac{10-(-15)}{5-2}=\frac{25}{3}[/tex]For line "b" the known points are (4,8) and (0,-6)
The slope of this line is
[tex]m_b=\frac{8-(-6)}{4-0}=\frac{14}{4}=\frac{7}{2}[/tex]The slope of line a is 25/3 and the slope of line b is 7/2
