The equivalent resistance is, Req1=R11+R21+R31Req1=31+35+21Req=0.4Ω The equivalent emf and resistance in parallel combination, Eeqreq=R1E1+R2E2−R3E3reqEeq=310+537−220reqEeq=15 Substitute the values in the above equation. 0.4Eeq=15Eeq=2V