Answer:
150 chicken eggs broke.
Explanation:
Let chicken eggs be represented by = c
Let duck eggs be represented by = d
An egg seller ordered 600 duck eggs and chicken eggs altogether.

The number of duck eggs was 2/5 of the total number of eggs.
=> d=
eggs.
So, c=

Some chicken eggs broke during delivery and the number of duck eggs became 8/15 of the total number of eggs.
Let x eggs broke.
Remaining were

And d=

=>

=>

=>

=>

x = 150
Hence, 150 chicken eggs broke.