The potential difference across ammeter and shunt is the same Let ia is the current. Flowing through ammeter and i the total current. So, a current i−ia will flow through shunt resistance
Potential difference across ammeter and shame resistance is the same That ia×R=(i−ia)×S r S=
iaR
i−ia
..........(i) Given ia=100A,i=750A,R=13Ω Hence, S=