Standard form:
Ax + By = C
First make it into slope-intercept form first:
y = mx + b
Find b by substituting the given to their respective positions:
-2 = 3(6) + b
-2 = 18 + b
-2 - 18 = b
-20 = b
Now the complete version is:
y = 3x - 20
Arrange the equation:
y = 3x - 20
-3x + y = -20
Easy :)