Answer:
4). The Washington Monument is 169.2-m tall. 
Step-by-step explanation:
4). We know this because...
person     1.8       0.7
----------  = -----  = -------
Wash.        x       65.8
We then know to cross-multiply to get:  
1.8(65.8) = 0.7x
Which simplifies down to:
118.44 = 0.7x 
x = 169.2
Answer:
5). The pond is 180ft wide. 
Step-by-step explanation:
5). We know this because...
90       120
-----  = -------
135        x
We then know to cross-multiply to get:
90x = 120(135)
Which simplifies down to:
90x = 16200
x = 180
Answer:
6). The height of the clock tower is 13ft 9in.
Step-by-step explanation:
6). We know this because...
person       5.5         4
----------  =  --------  = -----
clock            x          10
We then know to cross-multiply to get:
5.5(10) = 4x
Which simplifies down to:
55 = 4x
x = 13.75 (13 ft 9 in)