You posted a lot of questions. I'll do the first three to get you started.
==================================================
Problem 1
Answer: 55 square inches
Step-by-step explanation:
Draw a vertical line to enclose the un-shaded region. Think of it like adding fencing to enclose a paddock or backyard.
What results are two rectangles. The larger rectangle has area = length*width = 8*10 = 80 square inches.
The smaller unshaded rectangle inside has area of 5*5 = 25 square inches.
The difference of those areas is: 80-25 = 55
You have the correct answer. Nice work.
==================================================
Problem 2
Answer: 486 square feet
Step-by-step explanation:
Follow the same set of steps as done in the previous problem. Draw a vertical line to form a larger rectangle.
The larger rectangle has area of 18*31.5 = 567 square feet.
The smaller unshaded rectangle has area of 9*9 = 81 square feet.
Subtract those results to get the shaded region only: 567-81 = 486
==================================================
Problem 3
Answer: 5.6 square cm
Step-by-step explanation:
This time we don't have to add any extra lines to enclose the figure.
A = larger area = 6*2.4 = 14.4
B = smaller unshaded area = 2*4.4 = 8.8
C = A-B = 14.4-8.8 = 5.6 square cm
You have the correct answer. Nice work.