I know Ohm's law, Kirchhoff's laws, Power formulas

\(P=I^{2}R\)

\(P=\frac{E^{2}}{R}\)

\(P=EI\)

I tried finding R or I from \(R=\frac{P}{I^{2}}\)

This may be an easy example but I don't know I can't find R.

I'm solving harder problems, but can't find this one.

Thanks in advance.