Ineed . semir, sarah, and sungso decided to raise money for a local homeless shelter by working in a local deli. the deli agreed to donate to the shelter a portion of the profits from each meal the three sold. semir sold 3 times as many meals as sarah. sungso sold 2 more meals than sarah. the three decided to participate in a walkathon to raise additional money for the shelter. sarah walked 5 miles less than twice the number of miles that semir walked. they each collected $18 in pledges for every mile they walked. a. let n represent the number of miles semir walked. write an expression for the number of miles sarah walked and an expression for the amount of money sarah collected in pledges

According to the question, 
Let,
"n" represent the number of miles semir walked.
"y" represent the number of miles sarah walked.
Now, according to the question,

y = 2n - 5  this is your equation 
Also,
the question states, each of them collect $18 in pledges for every miles walked.

Given,
Sarah collected $450
Now, 

Using unitary method,

Sarah collects $18 for 1 mile
Sarah collects $1 for (1 / $18) mile
Sarah collects $450 for (1 / 18) * 450 mile
                                   = 25 miles
So, Sarah walks 25 miles.
Now,
Taking equation,
y = 2n - 5
Since, y is the no. of miles sarah walked, we can write 25 in place of "y" So,
(25) = 2n - 5
25 + 5 = 2n
30 = 2n
30 / 2 = n
15 = n

Since, "n" is the no. of miles that semir walked, Semir walked 15 miles.

121 pints. they had 176 and drank 55