Answer
As per the statement:
Height of the building(h)= 30 feet
Angle of elevation
= 41°
We have to find the distance of observer from the base of the building.
Using tangent ratio:

You can see the diagram as shown below.
Opposite side = height of the building = 30 feet.
Adjacent side = distance of observer from the base of the building = x (let)
Then;

0.86928673781 =

By cross multiply we have;

Divide by 0.86928673781 both sides we get;
x = 34.51 m
Therefore, the distance of observer from the base of the building is 34.51 m