The equation of the line below can be expressed in the form \frac{x}{a} + \frac{y}{b} = 1. Find a.
The lines passes through (5,8) and (-4,17).
Slope = [ 17 - 8 ] / [ -4 -5 ] = 9/-9 = -1
Equation of line using (5,8)
y = -1 (x -5) + 8
y = -x + 13
x + y = 13 divide through by 13
x / 13 + y /13 = 1
a = 13
+603 
