To solve this, set up a proportion with X being our unknown. If she cleans 12 houses in 10 hours, she cleans 27 houses in X hours. It will look like [tex] \frac{12}{10} = \frac{27}{x} [/tex].
Now cross-multiply to get 12x = 27(10) or 12x = 270. Divide by 12 on both sides to isolate x, X = 22.5.
It will take Kathy 22.5 hours to clean 27 houses. Must be some pretty small houses.
