## Math without words

### Instructions

1. Move the green points to change the values of $$a$$, $$b$$, $$c$$ and $$d$$.
2. Move the point marked in the following picture to select the intended operation (addition, subtraction, multiplication or division).
3. Observe the diagram for different values of $$a$$, $$b$$, $$c$$ and $$d$$.
4. The app displays a tip that helps find the value of the operatation. To see it, move from left to right the corresponding point.

The tip shows the value of the operation in a scheme at the right side of the app.
5. Find out the value of the operation.
6. To check your solution, move from left to right the corresponding point.