What would be the final temperature of the

Question

system if 20 g of lead at 100◦C are dropped
into 20 g of water at 30 ◦C in an insulated
container?

Answer 1

heat lost by lead + heat gained by water = 0

[mass Pb x specific heat Pb x (Tfinal-Tinitial)] + [mass H2O x specific heat H2O x (Tfinal-Tinitial)] = 0
Substitute all the number and solve for Tfinal. That's the only unknown in that long string.