The math help thread

Code:

if d>=P value: reduction = 0.7*(L/1300 + 8/9*n)*(d-P) + (n*d)
else:
-if l < 15: reduction = 1.3*(L/550 + n)*(d-P) + (n*d)
-else: (13/(L-2))*(L/550 + n)*(d-P) + (n*d)

I want to rewrite this to express d in terms of n, P, and L. Absolutely no idea how.