we have
Walker family= 20 L/H
James family = 35 L/H
Total time= 50h
total water= 1300L
let's x be the time walker family use the sprinkler
let's y be the time James family use the sprinkler
then the total time is given by
First equation
second equation
then the flow of water of is
Walker family = x*20
James Family = y*35
since the total flow is 1300L
then
now with the 2 system equation we can solve x and y
then
then
x+20=50
x=50-20=30
wich means
the walker family use the sprinkler for 30h
and
the James family use the sprinkler for 20h