Answer :
- Define $x$ as the number of invitations already mailed.
- Express the problem as an equation: $x + 12 = 20$.
- The equation representing the problem is $x + 12 = 20$.
- The answer is $\boxed{x+12=20}$.
### Explanation
1. Problem Analysis
Let's analyze the problem. Kayla is sending invitations to 20 friends. She has 12 invitations left to send. We need to find out how many invitations she has already mailed. Let $x$ be the number of invitations Kayla has already mailed. The total number of invitations is the sum of the invitations she has already mailed and the invitations she has left to send.
2. Forming the Equation
We can write the equation as: invitations mailed + invitations left = total invitations. Substituting the given values, we get $x + 12 = 20$.
3. Selecting the Correct Equation
Therefore, the equation needed to solve the word problem is $x + 12 = 20$.
4. Final Answer
The correct answer is A. $x+12=20$
### Examples
This type of problem is useful in everyday situations where you need to keep track of quantities. For example, if you are planning a bake sale and need to make 30 cookies, and you have already made 18, you can use the equation $x + 18 = 30$ to find out how many more cookies you need to bake. Understanding how to set up and solve these equations helps in managing resources and planning effectively.
- Express the problem as an equation: $x + 12 = 20$.
- The equation representing the problem is $x + 12 = 20$.
- The answer is $\boxed{x+12=20}$.
### Explanation
1. Problem Analysis
Let's analyze the problem. Kayla is sending invitations to 20 friends. She has 12 invitations left to send. We need to find out how many invitations she has already mailed. Let $x$ be the number of invitations Kayla has already mailed. The total number of invitations is the sum of the invitations she has already mailed and the invitations she has left to send.
2. Forming the Equation
We can write the equation as: invitations mailed + invitations left = total invitations. Substituting the given values, we get $x + 12 = 20$.
3. Selecting the Correct Equation
Therefore, the equation needed to solve the word problem is $x + 12 = 20$.
4. Final Answer
The correct answer is A. $x+12=20$
### Examples
This type of problem is useful in everyday situations where you need to keep track of quantities. For example, if you are planning a bake sale and need to make 30 cookies, and you have already made 18, you can use the equation $x + 18 = 30$ to find out how many more cookies you need to bake. Understanding how to set up and solve these equations helps in managing resources and planning effectively.
