2. b6 = 1/7

q = 6

b9 = b6 × q³

b9 = 216/7

b9 = 30 6/7

3. b3 = 20

b4 = 10

q = b4/b3 = 1/2

b5 = b4 × q

b5 = 5

4. b3 = 7√7

bn+1 = bn/√7

b4 = b3/√7

b4 = 7√7 / √7

b4 = 7