Answer: 4/11
Explanation:
The total number of books is 35+20=55, which will be the denominator, because the question is asking what fraction of all the books are hardcover. The number of hardcover books, 20, will be the numerator, so we end up with the fraction 20/55. 20 and 55 are both divisible by 5 (this means that when divided by 5, both numbers have a whole number quotient). 20/5= 4 and 55/5=11
So, the answer is 4/11