how much heat enrgy must be taken in 24 gram of water to reduce the temperature of 7 degrres celcius

Answer 1

To reduce temperature, heat energy must be removed, not "taken in".

Do you mean that you want to reduce the temperature BY 7 degrees? To reduce a temperature "OF 7 degrees" doesn't make sernse. Reduce it to what?

In this case, the amount that must be removed is
M*C*(deltaT) = 24*7 = 168 calories
since the specific heat C of water is 1.00