<h2>After full 30 days John will have 15 dozen speckled eggs to sell.</h2>
Step-by-step explanation:
Total number of hens John has = 51 hens
If there are 3 more hens, then total number of hens = 51 + 3 = 54 hens
Now, one third of the hens are speckled.
⇒ 18 hens are speckled.
Now, of the total 18 speckled hens lay speckled eggs.
⇒ 9 hens produce speckled eggs.
Now, one hen lays one egg in a day and a half.
⇒ 9 hens lay nine eggs in a day and a half .
⇒ 9 hens lay 180 (15 doz.) eggs in days
Hence, after full 30 days John will have 15 dozen speckled eggs to sell.