Answer:
4x+5y = 320
x+y = 70
Explanation:
We need one equation for the total number of shirts, and one for the total cost.
Total number = 70
So that means medium shirts + large shirts = 70
So our first equation is x+y = 70
Total cost = $320
So that means $4 times medium shirts + $5 times large shirts = 320
So our second equation is 4x+5y = 320