Knowing SOH CAH TOA, we can use Tangent (TOA) to figure this out.
The Tan(50) = opposite (Tree height) / Adjacent (90 feet)
Tan50= H (H is Tree Height)/90
H=90Tan(50)
H=about 107 feet.
Because the tree is 107 feet tall and the truck is only 90 feet away, Lenny should move his truck.
Hope this helps!