6n + 3 is equivalent to 3n + 2 + 3n + 1 because if you combine like terms you would get 6n + 3
(3n + 3n)
(2 + 1)
6n + 3
Now if you substitute 5 for n in both expressions you would get 33 for both
3(5) +2 + 3(5) + 1
15 + 2 + 15 + 1
33
Or for 6n + 3
6(5) + 3
30 + 3
33
