Answer:
17: 25in²
18. 53m² 
19. 21.6cm²
20. 20.8km²
Step-by-step explanation:
Formula for area of a parallelogram 
Area = Base Length x Height 
For 17 
Given Base Length: 5 in 
Given Height: 5 in
( Using the formula stated above ) area = 5 * 5 = 25
Hence the answer to #17 is 25in²
For 18
Given Base Length: 10 m 
Given Height: 5.3 m
( Using the formula stated above ) area = 5.3 * 10 = 53
Hence the answer to #18 is 53m² 
For 19 
Given Base Length:  5.4 cm 
Given Height: 4 cm 
( Using the formula stated above ) area = 5.4 * 4  = 21.6 
Hence the answer to #19 is 21.6cm²
For 20
Given Base Length: 5.2 km 
Given Height: 4 km 
( Using the formula stated above ) area = 5.2 * 4 = 20.8 km 
Hence the answer to #20 is 20.8km²