Susan completes 1/5of her science project each day. how many days will it take her to complete 5/6 of the project

About four days. If you need to be exact:

Lets start by giving them the same denominator (multiply 1/5 by 6 and 5/6 by 5)

=6/30 and 25/30

now lets simplify the fractions to have a denominator of 6 (divide the numerators and denominators by 5)

= 1.2/6, 5/6

divide the numerator 5 by 1.2 = 4.17

It will take 4.17 days to complete 5/6 of her project