Answer:
10.3
Step-by-step explanation:
So first you get the angle of T which is 25 degrees
The you use the law of sine

Then you get s = 10.34763268
Round to nearest tenth
s = 10.3
The white Christmas tree is 7.55m
Green Christmas tree is twice as tall as white Christmas tree: 7.55 * 2 = 15.1m
High golden Christmas tree: 15.1m - 0.454m = 14.646m
The total height of 3 Christmas trees is: 7.55m + 15.1m + 14.646m = 37.296m
Choose: A 37.296m
The question is worded poorly, but it looks like you have a lever in equilibrium, with a force x at a distance d from the fulcrum, and a force y at a distance L - d from the fulcrum. You already have the equilibrium formula for this situation:
xd = y(L - d)
If you know x, y, and d, you can solve for the length L.