Well, if you're allowed to use calculators, you can get S by using logarithmic identities:

log(A/B) = logA - logB

log(A*B) = logA + logB

a = logb <=> 10^a = b (for log base 10)

What I did:

.01 = 2.634(log[50.344/(625*S)])

.01 = 2.634[log(50.344) - log(625*S)]

.01 = 2.634[log(50.344) - (log625 + logS)]

.01/2.634 = log(50.344) - log625 - logS

.01/2.634 - log(50.344) + log625 = - logS (multiply by -1)

-.01/2.634 + log(50.344) - log625 = logS

10^(-.01/2.634 + log(50.344) - log625) = S

So, by my calculator: S = .0798493149