Answer:
B = 62.9ft
Explanation:
The distance where she is from the oak tree is 75ft,
The angle of elevation the stone makes with the top of the oak tree is 40°
The height of the tree is x ft
See attached document for better illustration
Using SOHCAHTOA,
Tanθ = opposite/ adjacent
θ = 40°
Opposite = x ft
Adjacent = 75ft
Tan40 = x / 75
X = 75 × tan40
X = 75 × 0.8390
X = 62.92ft
The height of the oak tree is 62.9ft