Question 165572
Let x=time it takes to type 20 pages when both are working together
So, 20/x=rate at which they work when working together
Jeanne types at the rate of 20/40=1/2 page per min
Jim types at the rate of 20/30=2/3 pages per min

Together they work at the rate of 1/2 + 2/3 =7/6 pages per min
So, our equation to solve is:
(7/6)*x=20  multiply each side by6
7x=120 
x=17.143 min

Another way:
7/6=20/x  multiply each side by 6x
7x=120-----------same as before

CK
(1/2)*17.143= 8.571 pages
(2/3)*17.143=11.429 pages
8.571 + 11.429=20
20=20


Hope this helps---ptaylor