Silver is reacted with excess mercury (II) chloride, producing a solid silver chloride precipitate. If the actual yield of 25.5...

Silver is reacted with excess mercury (II) chloride, producing a solid silver chloride precipitate. If the actual yield of 25.5 g silver chloride represents a 77% yield, how much silver was initially present?

Ag (s) + HgCl2 (aq) ------> AgCl (s) + Hg (l)

I already balanced the equation: 

2 Ag + HgCl2 -------> 2 AgCl + Hg

I am just so confused on how to solve this! What I know for sure is that the percent yield is actual yield/theoretical yield * (100), but I am not sure if that formula even matters in this question. I would love to learn though!