A. The order in which you define the variables isn't fixed. For the sake of this discussion, let's define them like this:
x = Number of bookshelves
y = Number of tables
B. Due to the total number of items to produce, we have the following inequality based on those variables.
x + y > 25
Additionally, you can create a second inequality concerning your budget for materials.
20x + 45y < 675
Moreover, you should also add that both values must not be negative, since you can't produce negative tables.
C. By analyzing the constraints and solving the system, you will find that the feasible region contains 4 vertices.
(0,0)
(18, 7)
(0, 15)
(33.75, 0) or (33, 0) if you prefer to round it.
Answer: D) randomized comparative design
Step-by-step explanation:
A randomized comparative design involves comparing two or more treatments and is characterized by an experiment intended to highlight differences between two groups or populations subjected to distinct conditions or treatments. In the scenario described, pre-existing data was juxtaposed with information collected after the alcohol dangers course.
Answer: a)
b) 
Step-by-step explanation:
a) To achieve an even total, there are 3 possible combinations:
1) Even, Even, Even, Even 
2) Even, Even, Odd, Odd
3) Odd, Odd, Odd, Odd 
Order is irrelevant
Summing these yields your final result: 
b) If one die shows a 2 and another a 3, while the remaining two can show any digits, there’s only one way to get a 2, one way for a 3, and six potential numbers for each of the other two dice.

Réponse:
Le domaine est l'ensemble des nombres réels
y ≤ 16
Explication étape par étape:
Le domaine est l'ensemble des valeurs x que le graphe couvre. Il n'y a aucune restriction sur les valeurs x. Le domaine est l'ensemble des nombres réels.
La plage est l'ensemble des valeurs y que le graphe couvre. Les valeurs y atteignent au maximum 16 au sommet de la parabole. Ainsi, la plage est y ≤ 16.