Why 110 TOEFL = 7.5 IELTS??????

First, there is no conversion. Neither IDP IELTS Australia, the British Council or the ITC will ever agree to compare the tests.

IELTS is a much tougher and much more objective test, and 7.5 on Academic Module is an exceptionally good score (I used to work as an IELTS examiner in China). I have also taken IELTS twice myself, and I have also taken the TOEFL two times: the last time for MBA application purposes.

IELTS components are well balanced, and human scored, i.e. a human examiner will look at every answer; every essay is read several times, and some of the oral interviews are listened to by several independent examiners. The score is very objective. Even then, if one thinks they deserve a different score, they can appeal the decision of the examiners, and another group of senior examiners will look at the work.

TOEFL is not a balanced test. iBT TOEFL speaking module is ridiculously unnatural and more difficult than the other components of the test. The rest of TOEFL is pretty straightforward; in China, New Oriental School has built a whole business around rigging TOEFL because there are certain things that are predictable. Whole armies of exam takers in the PRC come in prepared with all sorts of test taking tricks that have nothing to do with their language ability, and yet - allows them to score higher than their true level of language mastery permits.