Book- ManhattanGMAT prep-the new standard 4th edition
page no - 146 , verb tense,mood & voice problem set
question 19 : If Abraham Lincoln were born in Livonia, he cannot become the President of the United States.
solution(as in the book) : If Abraham Lincoln had been born in Livonia, he could not have become the President of the United States.
in this question both If...then clause are part of the underlined phrase. So how to decide which If..then Construction(given in the book)we have to use here. I mean when only If clause is underlined then we can change it according to the Then clause and vice versa but how to do that in this case.