The slope-intercept form: y= mx + b
m - slope
b - y-intercept
The formula of a slope:

We have the points (6, 2) and (5, 5). Substitute:

Therefore we have y = -3x + b.
Put the coordinates of the point (5, 5) to the equation:
5 = -3(5) + b
5 = -15 + b add 15 to both sides
20 = b
Answer: y = -3x + 20