Members of the choir are baking cookies for a fundraiser. it costs $2.25 to make a dozen cookies, and the choirs initial expenses were $15.75. they sell the cookies for $4.50 a dozen. how many dozen do that have to sell to cover their cost

Replace the number of dozens by x.

Expenses = 2.25x + 15.75
Money made = 4.50x

Compare the 2 equations :
2.25x + 15.75 = 4.50x

Solve for x by moving things around to isolate the x :

15.75 = 4.50x - 2.25x
15.75 = 2.25x
15.75/2.25 = x
...

Hope this helps!

She will need 5/8 bags for each square yard.