In indexed addressing mode
Effective address = address + contents of specified index register
In register indirect mode
Effective PC address = contents of register 'V'
Now , the address field value of an indexed addressing mode instruction to make it same as a register indirect mode instruction , we need to do is :
contents of register ' V ' = address + contents of index register
address = contents of register ' V ' - contents of index register
= 500-100
= 400