Solve the Triangle Equation: △ - 7 = 80

Linear Equations with Unknown Variables

Determine the numerical value of the triangle:

7=80 \triangle-7=80

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Determine the numerical value of the triangle:

7=80 \triangle-7=80

2

Step-by-step solution

The problem involves solving a simple algebraic equation:

7=80 \triangle - 7 = 80

  • Step 1: To solve for \triangle , we need to isolate it on one side of the equation. We can do this by adding 7 to both sides of the equation to reverse the subtraction.

7+7=80+7 \triangle - 7 + 7 = 80 + 7

This simplifies to:

=87 \triangle = 87

The value of the triangle symbol \triangle is 87 87 .

Therefore, the solution to the problem is =87 \triangle = 87 , which corresponds to choice 4 in the provided list of answer choices.

3

Final Answer

87 87

Key Points to Remember

Essential concepts to master this topic
  • Isolation Rule: Move constants to opposite side using inverse operations
  • Technique: Add 7 to both sides: 7+7=80+7 \triangle - 7 + 7 = 80 + 7
  • Check: Substitute back: 877=80 87 - 7 = 80 confirms our answer ✓

Common Mistakes

Avoid these frequent errors
  • Subtracting 7 from both sides instead of adding
    Don't subtract 7 from both sides when you see △ - 7 = 80! This gives △ = 73, which is wrong. The subtraction is already done in the equation. Always do the opposite operation to isolate the variable.

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 add 7 instead of subtract 7?

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Because the equation shows 7 \triangle - 7 , meaning 7 is being subtracted from the triangle. To undo subtraction, you add the same number to both sides!

What does the triangle symbol mean?

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The triangle \triangle is just a variable like x or y. It represents an unknown number we need to find. Don't let the unusual symbol confuse you!

Can I solve this equation differently?

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The standard method is adding 7 to both sides, but you could also think: "What number minus 7 equals 80?" Either way leads to =87 \triangle = 87 .

How do I check if 87 is really correct?

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Substitute 87 back into the original equation: 877=80 87 - 7 = 80 . Since this is true, our answer is correct!

What if I got 73 as my answer?

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If you got 73, you probably subtracted 7 from both sides instead of adding. Remember: check your answer by substituting: 737=6680 73 - 7 = 66 \neq 80 , so 73 is wrong.

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