Which of the following expressions could be used to find the difference between 238 b. c. and 15 b. c.?
15 - (-238)
-238 + (-15)
-15 - (-238)
-238 + 15

Essentially, the answer should be 238-15, because comparing the time difference between BC and AD is not different. But there is not such an option.

but we can look for an equivalent expression, and it's
-15 - (-238), since - (-... will give us a +, it is equivalent

-15+238

and we can rearrange

238-15

which is the same as I said in the beginning!

it only gets more complicated when you compare AD and BC!