calculate current nodal voltage method problem
Your KCL equations are incomplete.  For node 1, there are 3 currents involved and for node 2, there are 4 currents involved.

Using the first schematic, KCL at node 1 is:

$$I_1 + I_2 = 25A $$

KCL at node 2 is:

$$I_1 + I_3 + I_4 = 20A $$

Be careful to note that \$I_1\$ in the first equation is not the same as the \$I_1\$ in the second equation.

In the first equation,

$$I_1 = \frac{V_1}{4\Omega} $$

while in the second equation,

$$I_1 = \frac{V_2 - V_1}{10 \Omega} $$