<_title>Practice the addition operation
<_description>Answer some algebra questions
<_prerequisite>Simple addition. Can recognize written numbers
<_goal>In a limited time, find the sum of of two numbers. Introduction to simple in-line addition.
<_manual>A addition problem with two numbers is displayed. At the right of the equal sign, give the sum.
Use the left and right arrows to modify the sum, and the Enter key to check your answer.