The error is that he probably forgot the decimal point thus causing him to say '"hundred" instead of "and" for the decimal point.
Let's plug in (18,10) into each answer choice until we find the one that has it as a solution.
A) 2x - y = 26
2(18) - 10 = 26
36 - 10 = 26
26 = 26
Your answer is A.
I'll just do the rest to show that you the they are incorrect.
B) x + y = 18
18 + 10 = 18
28 ≠ 18
C) 2x - 2y = 36
2(18) - 2(10) = 36
36 - 20 = 36
16 ≠ 36
D) x - y = -28
18 - 10 = -28
8 ≠ -28
Your answer is A) 2x - y = 26.
Answer:

Step-by-step explanation:
First: multiply both sides by 4. 4 times c is 4c and the other sides cancels out as you are doing the inverse operation of division
Then, you have 
Subtract both sides by a squared
DO NOT TAKE THE SQUARE ROOT! This is because it is a squared plus 3b so you have to do the inverse of addition
From that you get 
Finally, divide both sides by 3.
You get 
A suitable solver will tell you instantly that the measure of b is 179.18 ft.
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If you want to do it yourself (meaning also with the aid of a calculator), you can use the Law of Sines. The given side is side "c", so you need the measure of angle C. That will be
180° -33° -63° = 84°
Then side "b" can be found from
b/sin(B) = c/sin(C)
b = c*sin(B)/sin(C)
b = (200 ft)*sin(63°)/sin(84°) ≈ 179.183 ft