we have the formula
[tex]\begin{gathered} V=RI \\ R=\frac{V}{I} \end{gathered}[/tex]substitute given values
[tex]R=\frac{40+30i}{-5+3i}[/tex]Remember that
To divide complex numbers, multiply both the numerator and denominator by the conjugate of the denominator
the conjugate of the denominator is (-5-3i)
so
[tex]\begin{gathered} R=\frac{40+30\imaginaryI}{-5+3\imaginaryI}*\frac{-5-3i}{-5-3i}=\frac{-40(5)-40(3i)-30i(5)-30i(3i)}{25-9i^2}=\frac{-200-120i-150i-90i^2}{25-9(-1)}=\frac{-110-270i}{34} \\ \\ R=\frac{-110-270\imaginaryI}{34} \\ simplify \\ R=\frac{-55-135\imaginaryI}{17} \end{gathered}[/tex]