Answer:
[tex]b/a\ hours[/tex]
Step-by-step explanation:
we know that
Betsy can clean a/b of the house in an hour
The whole house (100%) correspond to the number 1
so
using proportion
Find out how long will it take her to clean the whole house
[tex]\frac{(a/b)}{1}=\frac{1}{x} \\ \\x=1/(a/b)\\ \\x=b/a\ hours[/tex]