Answer:
x = 466.7 ft
Explanation:
The top left angle of the triangle is 59°, we know because we are shown that the exterior angle outside that part of the triangle is 31°, so 59° would make that a corner.
We can use Sin of this angle to find the missing side (in this case, the hypotenuse)
Sin 59° = 400/x
Solve for x
x(Sin 59°) = 400
x = 400/(Sin 59)
x = 466.7 (rounded to the nearest tenth)