Explanation:
The given line is
y = 3x - 1
3x - y - 1 = 0 .....i)
The line perpendicular to the line I Is
x + 3y + k = 0 .....ii)
The line II) passes through the point (7, 4) so
7 + 3 *4 + k = 0
7 + 12 + k = 0
19 + k = 0
I. e k = - 19
So the required equation is x + 3y - 19 = 0
Hope it will help :)❤