Answer :
- Substitute $x = 7$ into the expression $3x + 15$.
- Multiply $3$ by $7$ to get $21$.
- Add $21$ and $15$.
- The final result is $\boxed{36}$.
### Explanation
1. Understanding the problem
We are asked to evaluate the expression $3x + 15$ when $x = 7$. This means we need to substitute $7$ for $x$ in the expression and then simplify.
2. Substitution
Substitute $x = 7$ into the expression:$$3x + 15 = 3(7) + 15$$
3. Multiplication
Now, we perform the multiplication:$$3(7) = 21$$So the expression becomes:$$21 + 15$$
4. Addition
Finally, we add the two numbers:$$21 + 15 = 36$$
5. Final Answer
Therefore, the value of the expression $3x + 15$ when $x = 7$ is $36$.
### Examples
Imagine you're buying multiple items at a store. If each item costs $3 and you buy 7 of them, and there's an additional fixed cost of $15 for shipping, the total cost would be calculated using the same expression. This kind of calculation is useful in budgeting, understanding expenses, and making financial decisions.
- Multiply $3$ by $7$ to get $21$.
- Add $21$ and $15$.
- The final result is $\boxed{36}$.
### Explanation
1. Understanding the problem
We are asked to evaluate the expression $3x + 15$ when $x = 7$. This means we need to substitute $7$ for $x$ in the expression and then simplify.
2. Substitution
Substitute $x = 7$ into the expression:$$3x + 15 = 3(7) + 15$$
3. Multiplication
Now, we perform the multiplication:$$3(7) = 21$$So the expression becomes:$$21 + 15$$
4. Addition
Finally, we add the two numbers:$$21 + 15 = 36$$
5. Final Answer
Therefore, the value of the expression $3x + 15$ when $x = 7$ is $36$.
### Examples
Imagine you're buying multiple items at a store. If each item costs $3 and you buy 7 of them, and there's an additional fixed cost of $15 for shipping, the total cost would be calculated using the same expression. This kind of calculation is useful in budgeting, understanding expenses, and making financial decisions.
