Hi NesaBug,
Solutions:
Question 1:
To find the diameter you divide the circuference by pi.
18.84 / 3.14 = 6
Answer - 6ft.
Question 2:
To find the base you divide the area by the height
288 / 16 = 18
16 x 18 = 288
Answer - 18cm.
Question 3:
To find the last measure divide the product of the width and length by the total volume.
9 x 12 = 108
648 / 108 = 6
Answer - 6m.
Question 4:
To find the other sides just add and subtract and divide.
100 + 100 = 200
280 - 200 = 80
80 / 2 = 40
Answer - 40yd.