How to fill out.
First of all, select the number of equations with the drop-down list. The maximum number of equations allowed is 6. If your system has a large amount of equations, you should use the landscape screen orientation of your phone. Then, enter the coefficients of the variables of the equation. To remove a variable, enter "0" as its coefficient. To enter negative coefficients, use the "-" button.
To enter a simple fraction, use the "/" button, to enter a decimal fraction, use ".".
Examples
To input the system of equations $\{\table y+x=0.5-2y; -5x=1/8$ fill out the form as follows:

In this form $X_1$ corresponds to y, and $X_2$ corresponds to х. $3X_1+1X_2=0.5$ appeared after we entered all the coefficients (from the right side to the left).
In the second eqution ($0X_1+(-5)X_2 = 1/8$) - 0 before the first variable means that this variable doesn't exist in the equation.