Problem 20 resolved

I bid 3C to try to keep them out of a red suit and to play 3C rather than 2S. This worked out well; partner held

Q9x immaterial immaterial J (I think he had some detritus in the reds, but not much, maybe just the diamond jack... 5 hearts 4 diamonds I think?)

When I bid 3C, it actually went pass pass double. I got the jack of spades lead and made an overtrick.

Also, a note: from now on, we will be resolving problems in the comments, and posting short notes in future entries saying that the problems have been resolved.

Problems 16 and 17 resolved

On 16, I bid Stayman, and then bid 3H shortness after partner responded 2S. Partner made avery discouraging 4S call over that which I floated. Partner's hand was:

KJ7x KQx Kxx Kxx
(opposite)
98xx Axx AQJxx A

The spade Qx is on your left. Spades always makes five, while notrump will make five if you can guess the spades and 4 otherwise (assuming they lead a club.) So good guessers should play 3NT single-dummy, bad guessers 4S.

On 17, holding KQT97 9x KJ AQ86, after 1s 2h 2s 3c, I chose 4c. Partner bid 4H which I passed. This proved to be the right spot as partner held x AKJTx Qx Kxxxx. As I recall the heart hook was off and partner made 4.