Solve $\{\begin{array}{l}2x+y=7\\ x-y=2\end{array}$

Step-by-step solution

1. Step 1 · Elimination by addition
   $$3x=9$$

   The y terms are already opposites, so adding the equations removes y.

2. Step 2 · Divide by 3
   $$x=3$$

   Solve the resulting single-variable equation.

3. Step 3 · Back-substitution
   $$3-y=2\Rightarrow y=1$$

   Substitute x into the simpler original equation.