After the rocket has traveled a total distance of 300 feet, what is its vertical height above sea level? round the distance to the nearest foot.

I added a screenshot with the complete question along with its diagram.

vertical height is approximately 260 ft

Explanation:
We can note that the sea level, vertical height and the distance traveled by the rocket all form a right angled triangle.
This means that the special trig functions can be applied.
These functions are as follows:
sin θ = opposite / hypotenuse
cos θ = adjacent / hypotenuse
tan θ = opposite / adjacent

From the given we have:
θ = 60°
opposite is the vertical height that we want to find
hypotenuse = 300 ft

Applying the sin function, we can get the vertical height as follows:
sin (60) = opposite / 300
opposite = 300 * sin (60)
opposite = 259.807 which is approximately 260 ft

Hope this helps :)