Answer:
Denote the two points are A and B, the balloon is C. Then we have,
Side AB = 9 miles
Angle CAB (angle A) = 27 deg
Ange CBA (angle B) = 45 deg
=> Angle ACB (angle C) = 180 - 27 - 45 = 108 deg
Applying the sine theorem:
AB/sinC = BC/sinA
=> BC = AB x sinA/sinC = 9 x sin27/sin108 = 4.3 miles
Denote CH as the height from C to side AB (or distance from ground to balloon), we have:
CH = BC x sin B = 4.3 x sin*45 = ~3.04 miles
=> Distance from ground to balloon: ~3.04 miles
Hope this helps!
:)