Solve for missing variables in addition equations. This exercise is a typical pre-algebra quiz. An example could be shown as follows: 8 + y = 10. The value of ‘y’ i.e. the missing variable can be found by balancing the equation on both sides. In the current case, replacing the variable with 2 and adding to 10 brings it up to ten. Hence the value y=2. There are similar exercises in this quiz. After finding your answer, submit and check if you got it correct. This activity falls in line with pre-algebra which is studied in 3rd, 4th, 5th and 6th grade.