Andre is trying to solve this system of equations: {x+y=3
{4x=12−4y

Looking at the first equation, he thought, "The solution to the system is a pair of numbers that add up to 3. I wonder which two numbers they are."

Choose any two numbers that add up to 3. Let the first one be the x-value and the second one be the y-value.
The pair of values you chose is a solution to the first equation. Check if it is also a solution to the second equation. Then, pause for a brief discussion with your group.