Sheila has a plan to save $45 a month for 18 months so that she has $810 to remodel her bathroom. after 13 months sheila has saved $510. if the most sheila can possibly save is $70 per month, which of the following statements is true?

The answer is : Sheila must save $ 60 per month to achieve her goal.

The price of bathroom remodeling is $ 810.
After 13 months , she has                   $ 510

Which mean that she has a  $ 300 shortage to cover in 5 months.

Which meant she need to save :

$300/ 5  =
$ 60 / month in order to achieve her goal

Pardon me. to answer questions like this, we would have needed more information. for starters, two sentences from the excerpt that came with the question.