−n+(−3)+3n+5

-n + (-3) + 3n + 5 = 

-n - 3 + 3n + 5 =

-n + 3n - 3 + 5 =

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

3n - n + 5 - 3 =

 

2n + 2

 

Therefore, -n + (-3) = 3n + 5 = 2n + 2