Translation:Traveling to the Mediterranean Sea from my city is easy.
For the sentence above, if we follow Formal Standard, the sentence will be:
السَّفَرُ إلى البحرِ الأبيضِ المُتوسِّطِ مِن مدينتي سهلٌ.
"2as-safaru 2ilaa 2al-baHri 2al-2abyaDi 2al-mutawassiTi min madiinatii sahl(un)".
It is sahlun سهلٌ because the word is in the nominative case -- as خبر of السفر. And, it is 2al-2abyaDi الأبيضِ because it is in the genitive case, as نعت of البحر. So, if you have really heard 2al-2abyaDu الأبيضُ in the complete sentence audio, it is incorrect except if they spell it by the word-per-word (ie. outside the sentence, as there is no case involved).