What is the equation of a line that passes through the point (4, 2) and is perpendicular to the line whose equation is y= x/3−1 ?

Perpendicular lines have slopes that are opposite and reciprocal. Therefore, the line we are looking for has a -3 slope.
y= -3x+b

Now, we can substitute in the point given to find the intercept.
2= -3(4)+b
2= -12+b
b=14

Finally, put in everything we've found to finish the equation.
y= -3x+14