-3(5-15n) = 15(3n-2)

Use the distributive property on both sides:

-3(5 - 15n)  =  (-3)(5) - (-3)(15n)  =  -15 + 45n

15(3n - 2)  =  (15)(3n) - (15)(2)  =  45n - 30

-3(5 - 15n)  =  15(3n - 2)

-15 + 45n  =  45n - 30

Subtract 45n from both sides:

-15  =  -30

When the variable disappears, there are two cases:

if the left side equals the right side, then all numbers work;

if the left side doesn't equal the right side, then no numbers work.

Since the left side doesn't equal the right side, no numbers work; your answer is the empty set.