ANSWER
The linear equation is: y = 80x + 65
Te cost for 40 football jerseys: $3265
EXPLANATION
Let 'x' be the number of jerseys and 'y' the cost of x jerseys.
Each jersey costs $80, so the cost of x jerseys is 80x. There's also an extra fee for procesing of $65, which is the same no matter how many jerseys they buy.
Therefore, the cost 'y' of x jerseys is:
Now we want to know the cost of 40 football jerseys, so we just have to replace x by 40 and solve: