When the temperature is twice what it is now it will be 5 degrees warmer than it was when it was 4 degrees colder than it is now.
EXPLANATION AND SOLUTION
x is current temperature. y is 4 degrees colder, y=x-4.
Twice the current temperature is 2x. 2x-y=5 means there is 5 degrees' difference between twice the current temperature and 4 degrees below the current temperature: 2x-y=2x-(x-4)=5; 2x-x+4=5, x=1. The current temperature is 1 degree.