Based on the half-reactions and their respective standard reduction potentials below, what is the standard cell potential for the reaction that is expected to occur?

Question

Fe3+(aq) + e- → Fe2+(aq) 0.77 V
Sn4+(aq) + 2 e- → Sn2+(aq) 0.15 V
Pb2+(aq) + 2 e- → Pb(s) -0.13 V
ANSWER:
Based on the half-reactions and their respective standard reduction potentials below, what is the standard cell potential for the reaction that is expected to occur?
Fe3+(aq) + e- → Fe2+(aq) 0.77 V
Sn4+(aq) + 2 e- → Sn2+(aq) 0.15 V
Pb2+(aq) + 2 e- → Pb(s) -0.13 V
Answers:
0.64 V
0.90 V
0.28 V
1.03 V

Answer 1

i dont know where too begin

Answer 2

Same mixed up question as the next one. See my comments there.