Solve the Number Sequence: 21-3-6+9-5 Step by Step

Order of Operations with Integer Sequences

2136+95= 21-3-6+9-5=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Use the associative law and combine the subtraction terms into one term
00:11 Use the associative law again to cancel out two numbers from the exercise
00:21 We're left with a simple subtraction exercise
00:24 That's the solution!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

2136+95= 21-3-6+9-5=

2

Step-by-step solution

Due to the fact that the exercise only involves addition and subtraction operations, we will solve it from left to right:

213=18 21-3=18

186=12 18-6=12

12+9=21 12+9=21

215=16 21-5=16

3

Final Answer

16 16

Key Points to Remember

Essential concepts to master this topic
  • Left-to-Right Rule: Addition and subtraction have equal priority, solve sequentially
  • Step-by-Step: 21-3=18, then 18-6=12, then 12+9=21, finally 21-5=16
  • Check: Verify each calculation: 18-6=12, 12+9=21, 21-5=16 ✓

Common Mistakes

Avoid these frequent errors
  • Grouping addition and subtraction incorrectly
    Don't solve 21-(3-6+9-5) = 21-(-1) = 22! This changes the order and gives the wrong result. Always work left to right when operations have equal priority.

Practice Quiz

Test your knowledge with interactive questions

\( 0:7+1= \)

FAQ

Everything you need to know about this question

Why can't I just add all the positive numbers and subtract all the negative ones?

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Because the order matters! The expression 21-3-6+9-5 means you must follow the sequence exactly as written. Rearranging changes the problem completely.

What if I accidentally skip a step?

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Write down every single calculation! Even simple ones like 21-3=18. This prevents errors and makes it easy to find mistakes if your final answer is wrong.

Is there a faster way to solve this?

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You could combine like terms: 21+9365=3014=16 21 + 9 - 3 - 6 - 5 = 30 - 14 = 16 , but the left-to-right method is safer and less error-prone for beginners.

How do I know which operations to do first?

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Since this expression only has addition and subtraction, they have equal priority. Always work from left to right when operations have the same precedence level.

What if I get a different answer?

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Double-check each step! The most common errors are: mixing up signs, skipping steps, or not following left-to-right order. Redo each calculation carefully.

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