lets say that 1 typist types x pages in a minute then

1 typist in 2 minutes will type 2x pages

2 typists in 2 minutes will type 4x pages but we also know that 2 typists can type 2 pages in 2 minutes thus we have

4x = 2

x = 0.5 pages

1 typist types 0.5 pages per minute

5 typists will type 5*0.5 = 2.5 pages per minute

19 pages / 2.5 pages per minute = 19/2.5 minutes = 7.6 minutes

5 typist will type 19 page in 7.6 minutes.