Don't slide on the slope

Pick any two points on the line:

I picked the two points with the cross mark, (-6, 4) and (18, -6), though you could choose other points such as (6, -1).

Finding the slope:

May be $\frac{Rise}{Run}$

or $\frac{y_{2} - y_{1}}{x_{2} - x_{1}}$

which both equals to m or the slope

Substituting it with the formula above, using the points (-6, 4) and (18, -6):

$\frac{(-6) - 4}{18 - (-6)}$ = $\frac{-10}{24}$ = $\frac{-5}{12}$

And since it asks to write the answer as a +b:

-5 will be the a and 12 will be the b

a + b = -5 + 12 = 7

Hence, 7 is the answer