Three hours are enough to see everything in this art museum. (literally: If you have as many as three hours, you can see everything in this art museum.)
(a).
二万円も持って行けば足りるでしょう。
20,000 yen will probably be enough. (literally: If you take as much as 20,000 yen with you, it will probably be sufficient.)
(b).
ビールは二ダースも買っておけば大丈夫だ。
As for beer, if we buy two dozen, it will be enough (literally: we will be all right).
(c).
一週間もすれば歩けるようになります。
It will take no more than a week until you can walk (literally: until you become able to walk).
(d).
二、三回も聞けば大体分かる。
Listening two or three times is/will be sufficient for understanding most of it.
