What's wrong with my answer finding the resistance?

Question

This is the question and the solution:

Here's my answer:

My answer was incorrect, though I believe my analysis was correct. Can anyone point my mistake? I hope it's not with the signs.

Answer 1

I think I found it:

The mistake happened in Step 3: it should be:

$$ -(-2) + V_{src} + 2\cdot I = 0 \\ 2 -6 + 2\cdot I = 0\\ I = 2\mathrm{A} $$

Then, step 4:

$$ 1 - 2 - I_1 = 0 \\ I_1 = -1\,\mathrm{A} $$

Then, step 5:

$$ R = \dfrac{U}{I} = \dfrac{-2}{-1} = 2 \,\Omega $$