Answer :
No. You must distribute the 3 to the n and 6 on the second formula.
3n+6 and 3n+18 is not equivalent.
lets find out...
3(n + 6).....distribute the 3 through the parenthesis
3n + 18.....and this DOES NOT equal 3n + 6...so it is not equivalent
3(n + 6).....distribute the 3 through the parenthesis
3n + 18.....and this DOES NOT equal 3n + 6...so it is not equivalent