What would the predicted voltage be if four Zn(s)/ Zn2+(aq) // Ag+(aq) / C (s) cells were connected in series

Look up these values.

Zn(s) ==> Zn^2 + 2e.....E = ?
Ag^+ + e ==> Ag(s)......E = ?

Add the two E values to find Ecell, then multiply by 4 since they are in series.