All varieties of a certain brand of cookies are $3.50 A person buys peanut butter and chocolate chip cookies. Write an expression that tepresents the total cost.

To write an expression that represents the total cost of buying both peanut butter and chocolate chip cookies from the certain brand, we need to consider the quantities of each type of cookies purchased.

Let's assume that x represents the number of peanut butter cookies bought and y represents the number of chocolate chip cookies bought.

Since all varieties of the cookies are $3.50 each, the expression for the total cost will be:

Total cost = (cost per peanut butter cookie * number of peanut butter cookies) + (cost per chocolate chip cookie * number of chocolate chip cookies)

Or, in mathematical notation:

Total cost = (3.50 * x) + (3.50 * y)

Thus, the expression that represents the total cost is (3.50 * x) + (3.50 * y).