Corbin read 4/7 of the pages in his book. he has 42 pages left to read. how many pages did he read

If Corbin read 4/7 of his book, he has 3/7 of the book left to read.
This means that 3/7 of the book is equal to 42 pages.
42 ÷ 3 = 14
so 1/7 of the book is equal to 14 pages.
Since Corbin has read 4/7 of the book, 14 should be multiplied by 4.
14 × 4 = 56

Corbin has read 56 pages

Idon’t know actually is more difficult