The equation of the line passing through (1,11) and (4,5) can be expressed in the form x/a + y/b = 1. Find a.
Find slope = m = -2
point slope form
y-11 = -2 (x-1) re-arrange
y -11 = -2x+ 2
y + 2x = 13 divide by 13
x / (13/2) + y/13 = 1 a = 13/2