First, let's identify the like terms. 
2 and 17
2n and 3n
Next, you would need to combine them. Ex: Add 2n to both sides, and subtract 17 from both sides. 
2 - 2n = 3n + 17
2 = 5n + 17
-15 = 5n
Now, all you would need to do is isolate the n. To do this, you would divide both sides by 5. 
-15 = 5n
-3 = n
n = -3
The solution would be -3. 
I hope this helps!