He writes 30/3=<<30/3=10>>10 normal letters
Each letter is 20/10=<<20/10=2>>2 pages
So that is 2*10=<<2*10=20>>20 pages
His long letter takes 2*10=<<2*10=20>>20 minutes per page
So it is 80/20=<<80/20=4>>4 pages
So he writes 20+4=<<20+4=24>>24 pages
#### 24