Answer: 8 hours
Step-by-step explanation:
Let x be the time taken by each person to paint the fence.
Given: Tom and Becky can paint Jim's fence together in 12 hours.
Since all people paint at the same rate, then we have the following equation ;-

Thus, the time taken by each person to paint the fence alone = 24 hours
Now, the time taken by all three paint together:-

Hence, it would take 8 hours if all three paint together.
Constraints are simply the subjects of an objective function.
The inequality that represents the constraint is: 
Represent the number of hats with x, and the number of scarves with y.
From the question, we have:
- He spends 12 hours to knit a hat
- He spends 6 hours to knit a scarf
So, the equation of the total time spent is:

This time spent is not more than 20 hours.
So, the inequality is

Hence, the inequality that represents the constraint is: 
Read more about constraints at:
brainly.com/question/24574823
Answer:
Length, l=450 yards
Width, b=225 yards
Step-by-step explanation:
Let the long side be x and since the length is twice the width, then the width is half of that length hence 0.5x. Since we only have three parts to fence as one long side doesn't require fencing, then the perimeter will be given by x+0.5x+0.5x=2x=900 yards
X=900/2=450 yards for long side.
The short side is 0.5x hence 0.5*450=225 yards
In conclusion, the long side is 450 yards while short side is 225 yards.