3 phase transformer problem
Start with the equivalent circuit for a single phase transformer: -




Lp is the primary leakage inductance
Rp is the primary copper loss
Rc is the core losses due to eddy currents and hysteresis
Lm is the magnetization inductance
Ls is the secondary leakage inductance
Rs is the secondary copper loss


Picture from here.

Then think about the open circuit test; losses are 430 watts so, divide that by three to get the single phase losses and, recognize that those losses are consumed on the primary AND, the only lossy component that fits the bill is Rc. You know the voltage and you know the power so calculate Rc.

Then think about the short circuit test and where the power is dissipated. Your schooling should inform you that Rp and Rs are the main culprits because Rc will have little effect on power wasted with only 500 volts applied.

You can also modify the equivalent circuit I produced at this point; clearly the question isn't formed in such a way that Lp and Ls are significant so they can be shorted out AND, given that you only know the total power of the short circuit test you can assume all that waste is delivered by Rp so, make Rs a short circuit.

Can you take it from here?