For question number one:
We know that in similar triangles, corresponding sides are proportional.
In this scenario we have two triangles- one made by a stop sign and a shadow and one by a tree and its shadow.
The side of the triangle that is represented by the shadow of the stop sign is proportional to the side of the larger triangle represented by the shadow of the tree.
Also, the side of the smaller triangle that is represented by the height of the stop sign is proportional to the side of the bigger triangle represented by the height of the tree.
Using this information we can conclude that 12/42=18/h
By cross multiplying: 12h=42(18)
solve for h: (42)(18)/(12)=h
calculate: h=63
The height of the tree is 63 ft.