You can draw a diagram of the situation, representing it by a right triuangle.
In the right triangle the hypotenuse is the distance indicated by the radio signal, 1503 m, and the angle is 41°.
The opposed leg to 41° is the height of the ballon.
Then you can use the sine trigonometric function.
sine (41°) = opposed leg / hypotenuse = x / 1503 m => x = 1503m * sine(41°)
=> x = 986m.
Answer: 986m
