I think this problem is easy, but I can't do it.

answer: 2 A

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Node A is on the left, node B is on the right.

So,

A) \[ i_2 + i_4 = i_1 + i_3 \]

B) \[ i_3 + i_7 = i_6 + i_5 \]

\[i_1=\frac{v_1}{5}\], \[i_2=-3A\], \[i_3=\frac{v_1 - v_2}{20}\], \[i_4 = i_5 = 3 i_1 = \frac{3 v_1}{5}\], \[i_6=\frac{v_2}{10}\], \[i_7= 10 A\]

A) \[ -3 + \frac{3 v_1}{5} = \frac{v_1}{5} + \frac{v_1 - v_2}{20}\]

B) \[\frac{v_1 - v_2}{20} + 10 = \frac{v_2}{10} + \frac{3 v_1}{5}\]

I have this system of linear equations:

\[-60 = -7v_1 - v_2\]

\[200 = 13v_1 + 3v_2\]

\[v_1 = -2.5 V

v_2 = 77.5 V \]

\[i_1 =\frac{-2.5}{5} = -.5 A\]

Thanks for the help!