It’s b I did this lesson before hope that helps
Answer:

Step-by-step explanation:
Answer: A. 4
Im in high school this is simple math so. Your welcome
Answer: The required value is

Step-by-step explanation: The given functions are:

We are given to find the value of 
We know that, if s(x) and t(x) are any two functions of a variable x, then we have

Therefore, we have

Thus, the required value is
