I don't know how to come about this problem
Find the equation of the line that contains the point (4,1) and is perpendicular to the line y=-3x+4.
We'll write lines in the form y = m x + c, where m is the slope. The line you want is perpendicular to y = (-3)x + 4 which has slope -3. The slopes m and n of perpendicular lines satisfy mn = -1. So your line has slope m = (what?), and so equation y = m x + c for the m you just worked out and some value of c still unknown. But you know your line passes thro' the point (4,1): that is, x=4, y=1 satisfies y= m x + c. Substitute for x, y and m to find the value of c.