Solve the Equation: (-12) + ? = 30 | Finding the Missing Addend

Q: How do I remember which number to subtract from which?

Use this pattern: Sum - Known Addend = Missing Addend. So it's always 30 - (-12), not the other way around!

Q: Can I use the number line to check my answer?

Absolutely! Start at -12 and count forward 42 steps. You should land exactly on 30, confirming your answer is correct.

Q: What if I get confused with the negative signs?

Write out each step clearly: $ 30 - (-12) = 30 + 12 = 42 $. Take your time with sign changes - they're the trickiest part!

Q: Is there another way to solve this besides subtraction?

Yes! You can think: "What number plus -12 equals 30?" This helps you visualize moving from -12 to 30 on the number line.

Missing Addend with Negative Numbers

$(-12)+(?)=30$

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Complete the missing

00:03 Let's start from point (-12) on the negative (left) side of the axis

00:10 This is the desired number, let's find it on the axis

00:14 Let's find its distance from point (-12)

00:19 The direction of progression is to the right (positive)

00:44 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

$(-12)+(?)=30$

Step-by-step solution

Let's count on the number line the steps between -12 and 30.

We can see that 42 steps are required:

Final Answer

$42$

Key Points to Remember

Essential concepts to master this topic

Rule: To find missing addend, subtract known addend from sum
Technique: 30 - (-12) becomes 30 + 12 = 42
Check: Substitute back: (-12) + 42 = 30 ✓

Common Mistakes

Avoid these frequent errors

Adding instead of subtracting the known addend
Don't calculate (-12) + 30 = 18! This gives you the wrong operation and incorrect answer. Always subtract the known addend from the sum to find the missing addend.

Practice Quiz

Test your knowledge with interactive questions

a is negative number.

b is negative number.

What is the sum of a+b?

FAQ

Everything you need to know about this question

Why does subtracting a negative number become addition?

When you subtract a negative, it's the same as adding the positive! Think of it as removing a debt - if you remove owing $12, that's like gaining$ 12.

How do I remember which number to subtract from which?

Use this pattern: Sum - Known Addend = Missing Addend. So it's always 30 - (-12), not the other way around!

Can I use the number line to check my answer?

Absolutely! Start at -12 and count forward 42 steps. You should land exactly on 30, confirming your answer is correct.

What if I get confused with the negative signs?

Write out each step clearly: $30 - (-12) = 30 + 12 = 42$ . Take your time with sign changes - they're the trickiest part!

Is there another way to solve this besides subtraction?

Yes! You can think: "What number plus -12 equals 30?" This helps you visualize moving from -12 to 30 on the number line.

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