Answer:
The answer would be 2.7. Am not very sure though
Explanation:
So what you do is
for example the unkown number is x and the answer you get is y
12-x=y * -15=-140
-140/-15=9.33 (this is y the answer)
12-x=9.3
12-9.3=2.7
To check your answer
12-2.7=9.3
9.3 * -15=-139.5 if you round it then it would be -140