Sorry if my handwriting sloppy.
I showed all of it step by step.
Then mark it down by less then 1%, of by whatever the number would be.
X - (-20) = 5
When you subtract a negative, change it to addition:
X + 20 = 5
Subtract 20 from both sides:
X = -15
12.96 can be rounded to 13 if you're rounding to the nearest tenth and ones digit. If it is the tens digit, 12.96 can be rounded to 10.