Answer:
6b + 3a - 39n
Explanation:
Expanding using the distributive property :
-3(-2b + 5a + 7n - 10a + 6n +4a)
Multiply all values in the bracket by - 3
6b -15a - 21n + 30a - 18n - 12a
Collect like terms
6b - 15a + 30a - 12a - 21n - 18n
6b + 3a - 39n