It only took half as long to come back as it did to get there.
It took twice as long to get there as it did coming back.
ー It only took half as long to come back as it did to get there.
「行きに比べ帰りはたったの半分しかかからなかった。
take half as long to ... as it did to ...「〜に比べ半分しかかからなかった」という言い方です。
ー It took twice as long to get there as it did coming back.
「帰ってくるのに比べ、行きは２倍かかった。」
take twice as long to ... as it did ...ing「〜に比べ２倍かかった」という言い方です。
ご参考まで！
It only took me half the time to get home.
帰りは半分の時間で帰れました。
上記のように英語で表現することもできます。
half the time = 半分の時間
ほかには：
I took me twice as long to get there than to get back.
帰りに比べて行きは2倍も時間がかかりました。
お役に立てればうれしいです。
カナダ 
アメリカ合衆国 
