Solve for the Missing Number: 82 minus ? equals 7

Inverse Subtraction with Substitution Methods

If

=7 \colorbox{yellow}\\=7

Solve the following subtraction problem:

82= 82- \colorbox{yellow}\\=

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

If

=7 \colorbox{yellow}\\=7

Solve the following subtraction problem:

82= 82- \colorbox{yellow}\\=

2

Step-by-step solution

To solve this problem, we'll use the substitution method for the subtraction equation provided:

  • Step 1: Identify the value represented by the symbol. We are given that the yellow box equals 7.
  • Step 2: Substitute the value 7 into the subtraction problem: 82782 - 7.
  • Step 3: Perform the subtraction operation: 827=75 82 - 7 = 75

Therefore, the solution to the problem is 75 75 .

3

Final Answer

75 75

Key Points to Remember

Essential concepts to master this topic
  • Rule: Use substitution to replace symbols with known values
  • Technique: Convert 82 - ? = 7 to 82 - 7 = 75
  • Check: Verify by substituting: 82 - 75 = 7 ✓

Common Mistakes

Avoid these frequent errors
  • Confusing the position of the unknown value
    Don't think 82 - 7 = 82 when the yellow box equals 7! This ignores the subtraction operation completely. Always substitute the known value (7) into the correct position and perform the calculation: 82 - 7 = 75.

Practice Quiz

Test your knowledge with interactive questions

If we have 67 blocks in total, how many blocks will remain if we remove 5 tens and 4 ones?

FAQ

Everything you need to know about this question

Why do I substitute 7 for the yellow box in the subtraction problem?

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The yellow box is a symbol representing the same value in both equations. Since the first equation tells us the yellow box equals 7, we use that same value everywhere the symbol appears.

How do I know which number to subtract from which?

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Look at the order in the equation! In 82yellow box 82 - \text{yellow box} , you subtract the yellow box value (7) from 82, giving you 82 - 7 = 75.

What if I got 89 by adding instead of subtracting?

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This happens when you ignore the subtraction sign! Always pay attention to the operation symbol. The problem shows subtraction (-), not addition (+).

Can I check my answer a different way?

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Yes! You can work backwards: 75 + 7 = 82. If your answer plus 7 equals the original number (82), then you solved it correctly.

Why isn't the answer 70 or 80?

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These come from estimation errors. 70 would mean 82 - 12 = 70, and 80 would mean 82 - 2 = 80. Neither gives us the required result of 7 when we check our work.

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