Unique calculator app is free for one week only in the Google Play Store ($3 from the App Store)

You can scratch out digits if you want to change a number in the equation, draw the percentage symbol (%) to calculate a percentage, and a "?" can be used as a variable. You can also drag and drop numbers, and even if an equation uses multiple lines, it is still treated as one problem to be solved.

When you install the app, you'll go through a brief tutorial. Once you grasp the concept, you use your finger to write out equations on the touchscreen display of your iOS or Android phone. The equation is read by the app and quickly converts from your handwriting to an easy to read text. And just as fast, the answer appears on the screen. You can even do square roots, algebra, trigonometry and more. Calculations and answers can be saved, and any problem can be shared to friends, family or social media.

Now here's a math problem for you. What is $2.99-$2.99? The answer, of course, is zero. And that is how much you have to pay to install the the MyScript Calculator 2 app on your Android phone for the next week. After that, it will cost $2.99 to download from the Google Play Store. Those with an iOS device have to pay $2.99 for the app right now.