we have two points (0, 6) and (4, 3)
this can be represented as (x, y)
the equation of a straight line is
y = mx + c
slope = m = y2 - y1/ x2 - x1
x1 = 0, y1 = 6, x2 = 4 and y2 = 3
slope = 3 - 6 / 4 - 0
slope = -3/4
slope = -3/4
from the equation of a straight line
(y - y1) = m(x - x1)
y1 = 6 and x1 = 0
y - 6= -3/4(x - 0)
y - 6 = -3/4x + 0
y = -3/4x + 6
the error he made was that he used - 6 instead of +6 in the final answer