Subtraction: Simple subtraction of double digits

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

• Start with the equation: $\triangle - 9 = 20$
• Add 9 to both sides to isolate $\triangle$.

Now, let's carry out these steps:

Starting with the equation $\triangle - 9 = 20$.
To find $\triangle$, we add 9 to both sides:
$\triangle - 9 + 9 = 20 + 9$

Simplifying this gives us:
$\triangle = 29$

Therefore, the numerical value represented by $\triangle$ is $\boxed{29}$.

Looking at the multiple-choice options, we find that $29$ matches choice 3.

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

• Step 1: Add 8 to both sides of the equation $\triangle - 8 = 90$.
• Step 2: Simplify to determine the value of $\triangle$.

Now, let's work through each step:

Step 1: Add 8 to both sides of the equation:
$\triangle - 8 + 8 = 90 + 8$

Step 2: Simplify the equation:
$\triangle = 98$

This means the value of the triangle ($\triangle$) that satisfies the equation is $98$.

Therefore, the solution to the problem is $98$.

To solve the equation $\triangle - 3 = 70$, we will use basic algebra to isolate the value of $\triangle$.

We start by adding 3 to both sides of the equation to isolate $\triangle$:

$\triangle - 3 + 3 = 70 + 3$

Notice that $-3 + 3$ on the left side simplifies to 0, which leaves us with:

$\triangle = 70 + 3$

Now, perform the arithmetic on the right side:

$\triangle = 73$

Hence, the numerical value of the triangle is $73$.

The problem involves solving a simple algebraic equation:

$\triangle - 7 = 80$

• 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.

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

This simplifies to:

$\triangle = 87$

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

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