Answer:
6 hours
Step-by-step explanation:
What we must do is calculate the speed of each one,
Melissa in one hour plants 10 trees, that is 10/1 is her speed.
Jane in two hours plants 17 trees, that is 17/2 is her speed.
Now, we want to know the time it takes to plant 11 trees, so the sum of the previous speeds is equal to 111 / x
10/1 + 17/2 = 111 / x
18.5 = 111 / x
x = 111 / 18.5
x = 6
Which means that in 6 hours between the two they can plant 111 trees
