In our bank account example from the last exercise, we used the + operator to add the values balance and depositAmount:

double balance = 20000.99; double depositAmount = 1000.0; balance = balance + depositAmount; // balance now holds 21000.99

If we wanted to withdraw from the balance, we would use the - operator:

double withdrawAmount = 500; balance = balance - withdrawAmount; // balance now holds 19500.99

Addition and subtraction work with int type values as well! If we had 60 pictures of cats on our phone, and we took 24 more, we could use the following line of code to store 84 in numPicturesOfCats.

int numPicturesOfCats = 60 + 24;

What if we took one additional picture of our cat? We can reflect this change using an increment operator ++. When we append ++ to a number-based variable, it increases the value by 1. We also have the decrement operator, --, which decreases the value by 1.

// Take a picture numPicturesOfCats++ // Value is now 85 // Delete a picture numPicturesOfCats-- // Value is now 84



Create an int variable called animalsInZoo that holds the amount of zebras plus the amount of giraffes at the zoo.

Then, print your animalsInZoo variable.


Two of the zebras have been traded to a neighboring rival zoo. Subtract 2 from the number of zebras and store the result in a variable called numZebrasAfterTrade.

Then, print the numZebrasAfterTrade variable!

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