Solve the Expression: 18-2-5+9 Using Order of Operations

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

Because order matters in mathematics! The expression 18-2-5+9 means specific operations in a specific sequence. Rearranging changes the meaning and can give wrong answers in more complex problems.

Q: Is there a faster way to solve this?

You could rewrite it as 18+9-2-5 = 27-7 = 20, but be very careful with signs! The safest method is always left to right until you're confident with mental math.

Q: What if the expression had multiplication or division too?

Then you'd follow PEMDAS/BODMAS: Parentheses, Exponents, Multiplication/Division (left to right), then Addition/Subtraction (left to right). But this problem only has addition and subtraction!

Order of Operations with Multiple Subtractions

Solve:

$18-2-5+9$

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Understand the problem

Solve:

$18-2-5+9$

Step-by-step solution

To solve the expression $18-2-5+9$ , we follow the order of operations. Since there are only addition and subtraction operations, we can solve from left to right:

$18-2$ gives us $16$ .

Then, $16-5$ gives us $11$ .

Finally, $11+9$ gives us $20$ .

So, the correct answer is $20$ .

Final Answer

Key Points to Remember

Essential concepts to master this topic

Rule: With only addition and subtraction, work strictly left to right
Technique: Calculate step by step: 18-2=16, then 16-5=11, then 11+9=20
Check: Verify each step produces the correct intermediate result before continuing ✓

Common Mistakes

Avoid these frequent errors

Adding and subtracting in random order
Don't jump around and calculate 18+9-2-5 = 20! This ignores the left-to-right rule and can give wrong answers with different numbers. Always work systematically from left to right when you only have addition and subtraction.

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 all the positive numbers and subtract all the negative ones?

Because order matters in mathematics! The expression 18-2-5+9 means specific operations in a specific sequence. Rearranging changes the meaning and can give wrong answers in more complex problems.

What if I accidentally calculated 18-2-5+9 as 18-(2-5)+9?

That would give you 18-(-3)+9 = 18+3+9 = 30, which is wrong! Don't add parentheses where they don't exist. Work left to right as written.

Is there a faster way to solve this?

You could rewrite it as 18+9-2-5 = 27-7 = 20, but be very careful with signs! The safest method is always left to right until you're confident with mental math.

How do I keep track of negative and positive numbers?

Write down each step! Show 18-2=16, then 16-5=11, then 11+9=20. This prevents calculation errors and helps you spot mistakes quickly.

What if the expression had multiplication or division too?

Then you'd follow PEMDAS/BODMAS: Parentheses, Exponents, Multiplication/Division (left to right), then Addition/Subtraction (left to right). But this problem only has addition and subtraction!

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