From left to right, the answers are: 152, D(line e), C(obtuse), 44 degrees.
Now I feel guilty and sleezy. Giving answers alone without explanations
is something I almost never do, because it doesn't help anybody do
anything but cheat. But it's all I have time for right now. If a mod comes
along and decides to delete this because of no explanations, then let him
delete it. It'll serve us right, you and me both.
Edit: Misread the diagram, the previous answer was wrong.
Answer: x = 2
Step-by-step explanation:

Replace y in the first equation by the value of y in the second equation.

Answer:
x = 3
Step-by-step explanation:
10 + 2(7 - 9x) = 5(2x - 12)
10 + 14 - 18x = 10x - 60
24 - 18x = 10x - 60
+60 +60
-------------------------------------
84 - 18x = 10x
+18x +18x
-------------------------------------
84 = 28x
/28 /28
--------------------------------------
3 = x
The seats must be arranged in a 38 by 39 arrangement to have the minimum amount of seats used.
You can find this by finding the square root of 1450, which is 38.0788655293.