If x=students, the equation would be x=12 (x is less than of equal to twelve). I don’t know what you mean by constraints; perhaps if you explain more, I could help?
Answer:
(8,-1)
Step-by-step explanation:
Given : 

To Find: solution of given system of equations.
Solution:
Equation a : 
Equation b : 
Substitute the value of y from equation b in equation a
y from equation b : y = 7-x
Now substitute value of y in equation a
Thus equation a becomes:







⇒ x= -1 and x = 8
Now substitute values of x in equation b to obtains values of y
⇒ 
for x = -1
⇒ 
⇒ 
⇒ 
Thus (x,y)=(-1,8)
For x =8
⇒ 
⇒ 
⇒ 
Thus (x,y)=(8,-1)
Hence Option A is the correct solution .
Answer:
83.6155156
Step-by-step explanation:

Answer
I think its C which is 112
I think that this is right, but I assumed that the ceiling has the same dimensions as the wall you would need 4 gallons for 2 coats.
Work:
20x8= 160 (square feet for 1 wall)
160x5=800 (i assumed there are 4 walls and 1 ceiling)
800x2=1600 (you need 2 coats)
1600/400=4 (each gallon includes 400 square feet)