✨ ベストアンサー ✨
(16) Japan is not what it used to be.
it = Japan
used to be (以前は~だった)
(18) We found it very hard to put the plan into practice.
find O C 構文(OがCだとわかる) it は to不定詞句を指す
put ~ into practice (~を実行する)
(19) The tour cost me no more than 350 dollars.
no more than (たったの~)
ありがとうございます🙇