Well what exactly do you need help with?
Answer:
its 4
Step-by-step explanation:
a 1 = 3 , a n = a n - 1 + 2
because if you aply this to the shapes that you see at problem 21 you will see that it meaches them
Given:
A company wants to select 1 project from a set of 4 possible projects.
Consider the options are:
a.
b.
c.
d. 
To find:
The constraints that ensures only 1 will be selected.
Solution:
It is given that the company wants to select 1 project from a set of 4 possible projects. It means the sum of selected projects must be equal to 1.

Therefore, the correct option is (a).
If AB = 4 inches, AC would equal to 8 inches. The
correct answer between all the choices given is the last choice or letter D. I
am hoping that this answer has satisfied your query and it will be able to help
you in your endeavor, and if you would like, feel free to ask another question.