Answer:
15. 17.5 ft
16. XZY ~ RPQ only
Explanation:
15. The figure shows you the height of the object is 5/6 the length of its shadow. Then the height of the tree will be (5/6)·21 ft = 17 1/2 ft.
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16. Triangles are similar when they have all the same angles. In the given triangles, you have ...
angle X = angle R = 32° . . . . (no corresponding angle in the third triangle)
angle Z = angle P = 64°
angle Y = angle Q = 84°
The triangle vertices need to be named in the order in which they correspond, so we can say, for example, ...
triangle XZY ~ triangle RPQ