You must shoot the numbers with the [joystick and] fire button as they fall downward. If you hit two numbers in a row, an arithmetic problem that uses those two numbers appears at the bottom of the screen. You type in the answer, and if you're correct, the answer's value is added to your score.
Shoot 'em Up Math is a lightweight edutainment game published as type-in source code in Atari Basic. The game was published in Antic, Volume 2, Issue 4, July 1983, and was written by Andrew Silberstein.