A square of area 121 ft² will have a side dimension of √121 ft = 11 ft. The perimeter is the length of 4 sides, so is 44 ft.
You have the right idea and you are close to the correct answer. However that's not what your teacher is looking for in terms of steps.
The starting inequality is

She starts off selling 8 buckets. Then she sells b more to get a total of b+8
This total must be 20 or larger which is why I set b+8 greater than or equal to 20
Solve for b by subtracting 8 from both sides



So she needs to sell at least 12 more buckets to reach her goal
If you graphed this on a number line, then you would draw a closed circle at 12. Then shade to the right of the close circle.
They are simple linear equations with one unknown, lets tackle them, one step at the time solving for the unknown:
4x - 2(x - 5) = x + 13
4x - 2x + 10 = x + 13
2x + 10 = x + 13
2x - x = 13 - 10
x = 3
that is the solution.
3(6 - x) - 4 = 5x + 2(7x + 3)
18 - 3x - 4 = 5x + 14x + 6
14 - 3x = 19x + 6
14 - 6 = 19x + 3x
8 = 22x
x = 8/22 = 4/11
700x + 375(27 - x) = 15000
Solve for x
X=15 business class
Economy class 27-15=12