You first need to get the variable (k) on just one side. You can do this by subtracting 2k from both sides.
2k + 16 = 4k
16 = 2k
Now, you should be able to just divide both sides by 2 to get 8 = k (or k = 8, if that works better for you).
You can check your work by filling in 8 wherever you see k in the original problem.
2(8) + 16 = 4(8)
16 + 16 = 32