Let's apply the conservation of energy through the equation below:
Q for lead + Q for water = 0
So,
Q for lead = -Q for water
where
Q = mass*specific heat*(T₂ - T₁)
The specific heat of liquid water is 4.187 J/g·°C
Substituting the values:
(m)(0.129 J/g·°C)(17.9 - 91.6°C) = -(200 g)(4.187 J/g·°C)(17.9 - 15.5°C)
Solving for m,
m = 211.39 grams of lead