13Addition method (2/2)

Step 2: Removal of a variable by addition/subtraction.

Case 1: Addition of equations

The selected variable is contained once with positive sign and once with negative sign in the equations $\mathrm{I}$ and $\mathrm{II}$.

Now add the two equations $\mathrm{I}$ and $\mathrm{II}$ as above.

Case 2: Subtraction of the equations

The selected variable is contained twice with the same sign in the equations $\mathrm{I}$ and $\mathrm{II}$.

Now subtract the two equations $\mathrm{I}$ and $\mathrm{II}$ as above.

Step 3: Determine the values of the two variables

The new equation contains only one variable.

Solve it and find out its value.

By inserting this value into one of the equations $\mathrm{I}$ or $\mathrm{II}$, you determine the numerical value of the other variable.