I am given this circuit and asked to solve I with nodal analysis. I am mostly confused on how to set up the equations. Usually I have to solve for the voltages where I have 3 equations of v1-(voltage)/resitance but I don't see where this applies for finding the current I 

[![enter image description here](https://i.stack.imgur.com/QI4Vf.png)](https://i.stack.imgur.com/QI4Vf.png)

You are asked to solve a circuit shown in Fig. 1 (find unknown current I) using the nodal analysis.

2. Formulate a system of nodal equations for unknown voltages for the circuit shown in Fig. 1.