Question 1034851
You'll have to draw the diagram as it is not something I can do here...
Anyway, you'l have two triangles, a 45-45-90 and a 30-60-90...we can use the law of sines to find the hypotenuse of the 30-60-90 triangle by first showing how the outside triangle has angles of 45, 120, and 15 degrees.  
Call the hypotenuse of the inside triangle, c, so that
(sin 15)/100 = (sin 45)/c
which leads to 
c = 100 sin 45 / sin 15 = 273.2
The height of the balloon is sqrt(3)/2 times that...or 236.6 yards...