\(R=\dfrac{U}{I}=\dfrac{220}{0,5}=440\Omega\)
\(U'=U+\Delta U=220+50=270V\)
\(I'=\dfrac{U'}{R}=\dfrac{270}{440}=\dfrac{27}{44}A\)
\(\Delta I=I-I'=\dfrac{27}{44}-0,5=\dfrac{5}{44}A\)
\(\dfrac{U1}{U2}=\dfrac{I1}{I2}=>I2=\dfrac{\left(U2\cdot I1\right)}{U1}=\dfrac{\left(\left(220+50\right)\cdot0,5\right)}{220}=\dfrac{27}{44}A\)