Solve the Expression: 20-8-3+7 Step by Step

Q: Why can't I just add and subtract in any order I want?

Addition and subtraction have the same priority level, so you must work left to right. Changing the order changes the meaning of the expression and gives wrong answers!

Q: What if I accidentally group operations differently?

If you group incorrectly like $ 20-(8-3)+7 $, you'll get 22 instead of 16! Always follow the left-to-right rule for same-level operations.

Q: How do I remember the correct order?

Think of it like reading a book - you go from left to right! For expressions with only addition and subtraction, just work through each operation as you encounter it.

Q: Can I use parentheses to make it clearer?

Absolutely! Writing it as $ ((20-8)-3)+7 $ shows the order clearly. The answer stays the same, but it helps you see each step.

Order of Operations with Mixed Addition and Subtraction

Solve:

$20-8-3+7$

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Step-by-step written solution

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Understand the problem

Solve:

$20-8-3+7$

Step-by-step solution

To solve $20-8-3+7$ , follow these steps:

Start with the first operation: $20-8 = 12$ .
Next, subtract 3: $12-3 = 9$ .
Finally, add 7: $9+7 = 16$ .

Thus, the answer is $16$ .

Final Answer

Key Points to Remember

Essential concepts to master this topic

Rule: Work from left to right with same-level operations
Technique: Calculate step by step: 20-8=12, then 12-3=9, then 9+7=16
Check: Verify by substituting: (20-8-3+7) = (12-3+7) = (9+7) = 16 ✓

Common Mistakes

Avoid these frequent errors

Doing addition before subtraction
Don't add 3+7=10 first and then calculate 20-8-10=2! This ignores left-to-right order and gives the wrong answer. Always work from left to right when operations have the same priority level.

Practice Quiz

Test your knowledge with interactive questions

$$ 8 - 2 + 6 = $$

FAQ

Everything you need to know about this question

Why can't I just add and subtract in any order I want?

Addition and subtraction have the same priority level, so you must work left to right. Changing the order changes the meaning of the expression and gives wrong answers!

What if I accidentally group operations differently?

If you group incorrectly like $20-(8-3)+7$ , you'll get 22 instead of 16! Always follow the left-to-right rule for same-level operations.

How do I remember the correct order?

Think of it like reading a book - you go from left to right! For expressions with only addition and subtraction, just work through each operation as you encounter it.

Can I use parentheses to make it clearer?

Absolutely! Writing it as $((20-8)-3)+7$ shows the order clearly. The answer stays the same, but it helps you see each step.

What's the difference between this and PEMDAS?

This expression only has addition and subtraction (same level in PEMDAS), so we use the left-to-right rule. PEMDAS helps when you have different operation types mixed together.

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