Question 281487
an easier way to look at it is 

1/6+1/12=1/x or 

x/6+x/12=1
2x+x=12
3x=12
x=4
4 minutes for both to fill it
4/6+4/12=1
2/3+1/3=1
the first pipedoes 2/3 and the second pipe does 1/3