Answer:
9 minutes
Explanation:
To find how long it would take to read 6 pages, find the unit rate or the time to read 1 page.
Alejandro read 4 pages in 6 minutes. This means it takes him 6/4 = 1.5 minutes to read 1 page.
To read 6 pages it will take him 6*1.5 = 9 minutes.