Negative number
There are many methods to avoid the use of negative numbers.
Times
You always write a year as a positive number, even if it was before the year zero. The old Greek Archimedes lived from ca. 287 - 212 BC. To avoid writing negative years, the addition Before Christ is used. You may write
from −287 till −212
but that looks so unfriendly. If someone was born in 12 BC and died in 64 AD, you calculate his age as
12 + 64 = 76
Temperatures
In weather forecasts you talk about 7° below zero when it freezes. If it gets two degrees colder, you can calculate
−7° − 2° = 9° below zero
That is a rather strange method, but we are used to it. If it gets three degrees warmer, you calculate
−9° + 3° = 6° below zero
If the temperature rises even further, with ten degrees, than you can calculate
−6° + 10° = 4° above zero
Fortunately, most people do that correct.