In one hour, Addison mountain's temperature will decrease to 3/4  of its temperature. If the current temperature of the mountain is 84 degrees, what will the temperature decrease by?
In one hour, Addison mountain's temperature will decrease to 3/4 of the temperature it is now, meaning the temperature will decrease to 3/4*84=<<3/4*84=63>>63 degrees.
The temperature decrease will be 84-63=<<84-63=21>>21 degrees
#### 21