Division Sign Problem: Solve +2 ? +12 < 0

Let's pay attention to the exercise on the left side observing in particular the plus and minus signs.

The exercise looks like this:

$+:\text{?:}+=$

If we solve the equation from left to right, we observe that we first divide a positive number by an unidentified integer:

$+:\text{?}$

Since the next operation is also division by a positive number, we need a negative number in order for the result to be less than 0:

$+:-:+=$

$-:+=-$

- < 0

Therefore the answer is $-40$