Step by step
The question
Question: A diver is at −12 m.
She goes up 5 m.
Where is she now?
1 Write it as a sum
We start at −12.
Goes up means up: add 5.
−12 + 5
Sea level is 0.
Below it is negative.
−12 m: 12 m below sea level
goes up 5 → + 5
2 Work it out
Start at −12.
Go up 5.
Careful!
We start at −12, not at 12.
Keep the minus sign.
Careful: not 12 + 5 = 17 ✗
We land on −7 m.
= −7 m
So the answer is −7 m: 7 meters below sea level.
3 Check
Let's check: go back.
−7 minus 5 is −12, where we started.
So the answer is right!
−7 − 5 = −12
Let's look back.
First: write it as a sum.
Then: work it out.
Last: check.
Answer
= −7 m