Question 520542
not sure if that's a good hint


in the 15 min it takes working together, Rosita does 1/4 (15 min / 1 hr)
___ so Debbie does 3/4 in 15 min ___ she does 1/4 in 5 min (15 / 3)
___ so she can do 4/4 (the whole car) in 20 min (5 * 4)