Kirchhoff's first law states that the sum of all currents that enter an electrical circuit junction is $\displaystyle {0}$. The currents enter the junction have positive sign and the currents that leave the junction have a negative sign.

$\displaystyle {I}{1}+{I}{2}+\ldots+{I}{n}={0}$

If $\displaystyle {I}{1}$ and $\displaystyle {I}{2}$ enter a junction with $\displaystyle \frac{{7}}{{9}}$ amps and $\displaystyle \frac{{1}}{{9}}$ amps respectively, and $\displaystyle {I}{3}$ leave the junction with $\displaystyle -\frac{{1}}{{2}}$ amps, find the only other current in the junction $\displaystyle {I}{4}$.

$\displaystyle {I}{4}$ amps: