Equations in slope-intercept form follow a certain format.
y=mx+ b
In this format m is the slope and b is the y-intercept. The line has a slope of - 3 which means that we can substitute m=- 3.
y=- 3x+ b
To write a complete equation for this line, we also need to determine the y-intercept b. We can do that by substituting the given point (6,1) into the equation and solving for b.
