expr calculates. Give it a sum, and it writes the answer.

Put a space before and after the sign. Write \* to multiply: on this computer, * alone has a different job (Chapter 5 explains it), and the backslash \ makes sure that the * gets to expr unchanged.

1. What is 12 times 12?
2. What is 250 plus 175? This page does not show the sign for plus. Make a guess.
3. Think before you type: what does expr 19+23 write?