A transformer operating at primary voltage 8kV and secondary...

Since the transformer is assumed to be purely resistive, the power of the transformer can be calculated with $P = \dfrac{{V}^{2}}{R}$. Therefore,

For the primary coil,

$P = \dfrac{{\left(8 \times {10}^{3}\right)}^{2}}{{R}_{P}} = 80 \times {10}^{3}W$

$⇒ {R}_{P} = 800Ω$

For the secondary coil,

$P = \dfrac{{\left(160\right)}^{2}}{{R}_{S}} = 80 \times {10}^{3}W$

$⇒ {R}_{S} = 0 . 32Ω$