Answer:
She will buy new bottles after 6 weeks.
Explanation:
Valerie required 12 oz per week for her laundry
He have total 75 oz in a bottle.
Lets take she will buy new bottle after x weeks.
Fluid required for 1 week = 12 oz/week
Fluid required for x week = 12 x oz/week
Given that total she have 75 oz
So now by equating
12 x = 75
x=6.25 weeks
It means that she will buy new bottles after 6 weeks.