Mark M. raises a valid question. As written, the equation looks like -1/(3x) - 5.
I'll assume the equation is y = - (1/3)x -5.
Linear equations can be written in the form y - mx + b, where m is the slope and b is the y-intercept, the value of y when x = 0.
A perpendicular line has a slope that is the negative reciprocal of the original slope, -(1/3) in this case. That means a line perpendicular would have a slope of 3, so we can write y - 3x + b. We don't know b yet, but any line with this slope will be perpendicular. The value of b simply shits this line left of right.
We find b by entering the one point we know is on the line, (12,0). Just enter these values of (x,y) into the equation:
12 = 3*0 + b
b = 12
So the line perpendicular to y = -(1/3)x - 5 is y = 3x + 12