Answer:
1) She would save money if she paid per-visit. She would only pay %72 of what she pays monthly
2) She goes to the gym %43 of the days of the year
3) If she goes every day to the gym, she would spend $150 per month if she paid per-visit, that is %67 more than the $90 monthly fee
Step-by-step explanation:
1) She goes to the gym 3 times per week, so she goes 3*4.3 = 12.9 times per month. Thus, if she were to pay only $5 per day instead of a monthly membership, she would spend 5*12.9 = $64.5 per month.
Therefore, she would save money if she paid on a per visit basis, by using a rule of three, we can conclude that she would spend only 64.5*100/90 = %72 of her monthly $90 fee.
2) If she goes 3 times per week, she is going 3 days out of 7, thus, she is going 3*100/7 = %43 days of the year.
3) If a month has 30 days, then she would spend 30*5 = $150 if she paid per-visit and she went to the gym every day. That is $60 more than the $90 she spends for her monthly membership, in other words, it is 60*100/90 = %67 more than the %90 monthly rate.
, so our solutions are 
and 
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