To solve the first equation:

7 ÷ 2 / 21 = 9

First, divide 7 by 2:

7 ÷ 2 = 3.5

Next, divide 3.5 by 21:

3.5 ÷ 21 = 0.1667

So, the missing number is 0.1667.

To solve the second equation:

14 / x ÷ 2 / 5 = 7/6

First, divide 14 by the unknown number x:

14 / x

Then, divide the result by 2:

(14 / x) ÷ 2

Finally, divide that result by 5:

((14 / x) ÷ 2) ÷ 5 = 7/6

Unfortunately, additional information is needed in order to find the value of x.