TypeError: unsupported operand type(s) for -: 'str' and 'str'?
<p>I'm new to programming and can't figure out how to fix this error:</p>

<pre class="lang-none prettyprint-override"><code>Traceback (most recent call last):
  File "/Users/aubreyoleary/Documents/Cashier.py", line 31, in &lt;module&gt;
    changePennies = int((amountReceived - amountDue) * 100)
TypeError: unsupported operand type(s) for -: 'str' and 'str'
</code></pre>

<p>My code:</p>

<pre><code>import math

class Cashier:

    def getDollars(self, x):
        return x / 100

    def getQuarters(self, x):
        y = x % 100
        return y / 25

    def getDimes(self, x):
        y = x % 100
        return y % 10

    def getNickels(self, x):
        y = x % 100
        return y % 5

    def getPennies(self, x):
        y = x * 1
        return y

while True:

    thecashier = Cashier()

    amountDue = input("Please enter amount due: ")
    amountReceived = input("Please enter amount received: ")

    changePennies = int((amountReceived - amountDue) * 100)

    print(thecashier.getPennies(changePennies))
    print(thecashier.getDollars(changePennies))
    print(thecashier.getQuarters(changePennies))
    print(thecashier.getDimes(changePennies))
    print(thecashier.getNickels(changePennies))

    choice = input("Do you want to continue &lt;yes&gt; &lt;no&gt;? ")
    if (choice == "no"):
        print("Have a nice day. ")
        break
</code></pre>