Math Quizer

A Math quizzing app to improve mathematic skills and while still using basic mathematics promote algebraic thought. This app has 10 different quizzes type questions, which are below. The ? is what you must answer.

8 + 8 = ?
8 - 8 = ?
8 x 8 = ?
8 / 8 = ?
8 / ? = 16
8 - ? = 0
8 x ? = 64
8 / ? = 1
? - 8 = 0
? / 8 = 1

For each category you can have the numbers be 1-4 digits.
1 digit : 0-9
2 digits: 0-99
3 digits: 0-999
4 digits: 0-9,999