Final answer:
To calculate 5x when x equals 3, we multiply 5 by 3 to get 15, making b) 15 the correct answer.
Step-by-step explanation:
The question asks us to calculate the value of 5x when x = 3. To find this, we simply multiply the number 5 by the value of x given in the problem.
5x = 5 * 3
So the calculation becomes:
5 * 3 = 15
Therefore, the correct answer is b) 15.