Solve Triangle + 79 = 80: Find the Symbol's Value

Linear Equations with Symbol Variables

Determine the numerical value of the triangle:

+79=80 \triangle+79=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:

+79=80 \triangle+79=80

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Rewrite the given equation by subtracting 79 from both sides.
  • Step 2: Simplify the result to isolate and determine the value of the triangle ()(\triangle).

Now, let's work through each step:
Step 1: We start with the equation +79=80 \triangle + 79 = 80 . To isolate \triangle, subtract 79 from both sides:
+7979=8079 \triangle + 79 - 79 = 80 - 79 .

Step 2: Simplify the result:
=1 \triangle = 1 .

Therefore, the numerical value of the triangle is =1 \triangle = 1 . This corresponds with choice 3.

3

Final Answer

1 1

Key Points to Remember

Essential concepts to master this topic
  • Isolation Rule: Move the constant to isolate the unknown variable
  • Technique: Subtract 79 from both sides: +7979=8079 \triangle + 79 - 79 = 80 - 79
  • Check: Substitute back into original equation: 1+79=80 1 + 79 = 80

Common Mistakes

Avoid these frequent errors
  • Adding instead of subtracting the constant
    Don't add 79 to both sides when it's already being added to the triangle = =159 \triangle = 159 ! This makes the equation unbalanced and gives a wrong answer. Always do the opposite operation to cancel out the constant term.

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 subtract 79 instead of doing something else?

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Because 79 is being added to the triangle, you need to do the opposite operation (subtraction) to cancel it out. This is the key principle of solving equations!

What if the triangle represented a different number?

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The triangle is just a placeholder for an unknown number, like using x or y. The solving process stays exactly the same - isolate the unknown by doing opposite operations.

Can I solve this in my head?

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Absolutely! Since 79+1=80 79 + 1 = 80 , you can see that the triangle must equal 1. But showing the algebraic steps helps you solve harder problems later.

What if I get a negative answer?

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Negative answers are completely valid! For example, if the equation was +85=80 \triangle + 85 = 80 , then =5 \triangle = -5 would be correct.

How do I check if my answer is right?

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Substitute your answer back into the original equation. If 1+79=80 1 + 79 = 80 is true, then your answer is correct!

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