Let M and N be constants. The graphs of the lines x+5y=7 and 15x+MY=N are perpendicular and intersect at (-8,3) Enter the ordered pair (M,N)
Equation of first line: y = -1/5*x + 7/5:
Equation of second line: y - 3 = -5(x + 8)
y = -5x - 37.
3y = -15x - 111
15x + 3y = -111
(M,N) = (3,-111)