Jawabanmu

2014-06-11T22:05:29+07:00
Qlepas = Qserap
(20 x (40-ta))gelas + (m x c x (40-ta))air = (m x c x (ta-0)) es 
2014-06-11T23:10:23+07:00
Q lepas = q serap
m c Δ t  = m c Δt + m L
200 1 (40-x) = 40 1 (x-0) + 40 80
8000 - 200x = 40x + 3200
240 x = 4800
x = 20