Grammar `1問

Words cannot express how pleased(adjective) I am.<--Correct

"How+ pleased(adjective) means " 有多+高興".
"How" and "pleased" are together in this sentence.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I did not know where you went. Correct.
( This is a statement, not a QUESTION!)<====
點解又唔系
I did not know where did you go. <--WRONG!!
Where did you go?<----------This is a question.
(You cannot throw a question into a statement in English grammar.)
Let me show you some examples.
~~~~
1) I have no idea where she lives. <--------------Correct
I have no idea where does she live.<------------Wrong
Where does she live?<------------A question here!!

2) She doesn't know how old I am. <----------Correct
She doesn't know how old am I.<--------------Wrong
How old am I? <-----------------Here is a question!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I do not know HOW TALL she is.
I do not know HOW he did it.
I do not know HOW HEAVY the fat boy IS.
I do not know HOW BIG his room is.
( JUST MAKE SURE YOU WON'T PUT ANY QUESTIONS INTO ANY STATEMENTS.)
Questions:
How tall is she?
How did he do it?
How heavy is the fat boy?
How big is his room?

By the way, "How pleased am I?" is a question. ( How +an adjective)

Bye

唔需要想得太複雜：
你想想一d你識既句子結構如：
I don't know how long it is.
I don't know how many it is.
I don't know how much it is.
I don't know how far it is.
I don't know how old you are.

你唔會咁寫：
I don't know how it is long.
I don't know how it is many.
I don't know how it is much.
I don't know how it is far.
I don't know how you are old.

正如：
Words cannot express how pleased I am.
唔會寫：
Words cannot express how I am pleased.

cannot後用 express

how後接形容詞 pleased

不是問句，為何用 did you go

配搭，不是「配答」

配搭不是這個原因，是因為 how後是規定用形容詞

2009-08-26 00:41:31 補充：
在你的例子，how後是規定用形容詞

Two statements are wrong.
cannot 一定跟著 infinitive
so cannot express

I think the correct statement should be :
Words cannot express how pleased I am.