the perpendicular line will have slope = 9/4, the negative inverse of the given line's slope of -4/9. Just change the sign and flip the fraction upside down.
the x intercept of 36 is the point (0,36) plug that point into the point slope formula to get
0 = (9/4)36 + b where b is the y intercept
the perpendicular line equation is
y=(9/4)x - 81 in slope intercept form