Answer :
't' is the temperature before it decreased.
The temperature decreases by 15.2, so we subtract 15.2.
The result after we subtract is -12.8, so that's what it equals.
So we have:
t - 15.2 = -12.8
The temperature decreases by 15.2, so we subtract 15.2.
The result after we subtract is -12.8, so that's what it equals.
So we have:
t - 15.2 = -12.8