To solve for x, we can set up the proportion:

5/6 = x/5/12

Cross multiply to solve for x:

5 5/12 = 6 x
25/12 = 6x
x = 25/72

Now, to solve for x in the second proportion:

x / 4/9 = 8/27

Simplify by multiplying by the reciprocal:

x * 9/4 = 8/27
9x/4 = 8/27

Cross multiply to solve for x:

27 9x = 4 8
243x = 32

Now divide by 243 to solve for x:

x = 32/243

Therefore, x = 25/72 in the first proportion and x = 32/243 in the second proportion.