Jawabanmu

2014-04-16T20:09:38+07:00
ΔT=Q:(m.c)
ΔT=84000:(0,5.4200)
ΔT=84000:21000
ΔT=4

Suhu akhir = T₁+ΔT
                 = 20+4
                 = 24
2014-04-16T20:12:23+07:00
84kj = 84000j
500g = 0,5 kg

Q = m.c.Δt
84000 = 0,5.4200.Δt
84000 =2.100.Δt
Δt =  84000
      _________
          2100
Δt =40

Δt = t2 - t1
40= t2 - 20
t2= 40+20
t2 =60