The part that I don't understand in the calculations is this:

q(lead) = 0.128 J/g °C x 150g x (28.8°C - 100°C) = -1.37 E3 J

Why do they subtract 100 from 28.8? From my present understanding, 100 degrees is the initial temperature of the lead and 28.8 degrees is the initial temperature of water; shouldn't they subtract 100 degrees from 22 degrees?

Thank you.