To solve the problem, let's break it down step-by-step.
1. Understanding the Problem:
- We know the product of two numbers is 21.
- We are given that the first number is 3.
- We need to find out which equation represents this situation and what the second number is.
2. Setting Up the Equation:
- Let the second number be [tex]\(x\)[/tex].
- The product of the two numbers (which are 3 and [tex]\(x\)[/tex]) is 21.
- Thus, we can express this as: [tex]\(3 \cdot x = 21\)[/tex].
3. Solving for [tex]\(x\)[/tex]:
- To find the second number, we need to solve the equation: [tex]\(3x = 21\)[/tex].
- Divide both sides of the equation by 3 to isolate [tex]\(x\)[/tex]:
[tex]\[
x = \frac{21}{3}
\][/tex]
- Simplify the right side:
[tex]\[
x = 7
\][/tex]
4. Conclusion:
- The equation that represents this situation is [tex]\(3x = 21\)[/tex].
- The second number, [tex]\(x\)[/tex], is 7.
Therefore, the correct answer is:
B. The equation that represents this situation is [tex]\(3x = 21\)[/tex]. The second number is 7.
