To determine how much money Jenna has left we first need to determine how much she had before the purchase. To do that we will have to multiply the value of the money she has, by the amount of that type of money. For example, she has 8 one-dollar bills, so we have to multiply 8 by the value of a one-dollar bill. We then need to add the result of all these products, this is done below:

Now we need to subtract the cost of the smoothie by the money she had before the purchase:

After the purchase, Jenna has $4.15 left.