Answer:
A
Step-by-step explanation:
it takes 45 hours to plant 100 trees, so his rate is 100/45 trees per hour.
and it takes rose 40 hrs to plant the 100 trees, so her rate is 100/40 trees per hour
So add those together to get (100/45+100/40)
and then multiply them by P(which is in hours) to equal 100
(100/45+100/40)p=100
then divide by 100 both sides to get
p/45+p/40=1
