Ineed solving number 1. could anyone go over the steps?

Well if the girl sold the same number of larges but one less small and she made $5 less, then you know that the small boxes are $5. From there take the equation 2s + 7L =52 and subtract 10 from 52 (the two small boxes equal 10) You're left over with 7L= 42 so then do 42/7 = $6 per big box

So First of you'd make equations using what we know 3s+7L=57 2s+7L=52
so because these equations have only a difference of one small box this tells us that one small box is $5 so then using the second equation we can find the value of the large boxes 2(5)+7L=52   7L=42. 42/7=6 one large box is $6.