Answer:
12.25s + 3.99 = 77.49 would be your equation used to find the amount of shirts purchased.
When we solve the equation, we get 6 which is the quantity of shirts Gartland purchased.
Explanation:
We know the shirts were 12.25 but we didnt know how much she pruchased leaving our shirts (s) unknown.
We added 3.99 for shipping and our total cost was 77.49
We do 12.25s + 3.99 (shipping) = 77.40 total cost