Exercises 3.2-2 solution incorrectly says "Prove equation (3.15)"

[fatestapestry]

The solution starts with:

Prove equation (3.15).

Actually, the question is:

Prove equation (3.16).

I'm looking at the 3rd edition.

[redcurry]

It looks like this book is based on the second edition, which does say "Prove equation (3.15)."