Luis's Random Calculation
Luis has a simple calculator that has buttons for the digits 0 through 9, each of the 4 basic operations \((+, - \times, \div)\), and an '=' button. Luis pushes a digit followed by the '+' sign, followed by another digit, followed by the '-' sign, followed by another digit and then the '=' sign. How many different answers could Luis get?
Details and assumptions
The 3 digits pressed can be the same, e.g. \( 1 + 1 - 2 \) is valid.