Tolong mo 13 ya, pakai jalan ya...

Q total = Q₁ + Q₂
Q total = {m × c × (T₂ - T₁)} + (m × L)
20.625 kal = {m × 0,5 kal/g°C × (0°C - (-5)°C} + (m × 80 kal/g)
20.625 kal = {m × 0,5 kal/g°C × (0°C - + 5°C} + (m × 80 kal/g)
20.625 kal = (m × 0,5 kal/g°C × 5°C) + (m × 80 kal/g)
20.625 kal = (m × 2,5 kal/g) + (m × 80 kal/g)
20.625 kal = m × 82,5 kal/g
m = 20.625 kal ÷ 82,5 kal/g
m = 250 g

c.250g
maaf jika salah ya