cold water =10°c×3=30°c
result =20°c
hot water =20°C+30°C
=50°c
cold water is x 3 because a question says that the mass is 3 times the cold water so it is 3 into 10 it is 30
30 is added with result because as the property says when hot water is put to the cold water the temperature decrease of the hot water and temperature is increased in the cold water so the result is 20 so we at we will add 20 and 30 so we will get 50 Celsius