Remember that the point where the plane is located is A, and the altitude to the sea level is AR.

According to sine theorem, AQ = 8000/ sine (90-32) degrees.

AP=8000/sin45 degrees

PR/sin45 degrees =AP/sin90 degrees.

QR/ sine 32 degrees = AQ/ sine 90 degrees.

PQ=PR-QR=8000-8000sin32 degrees /sin58 degrees = 3000.3m.