Solving Systems of Equations: Substitution Systems of equations can be solved by substituting an expression from one equation into the other equation. Examples: 1. 3 =2−4 = − + 9 Since y is equal to both (! − 4) (− + 9), those two expressions are equal to each other... 32 − 4 = − + 9 To solve the system, solve for x, and then substitute your solution for x into one of your original equations and solve for y. 2. = 2 − 1 3 + 2 = 6 Since y is isolated in the first equation, we can substitute "2 − 1" wherever we see y in the second equation: 3+22−1 =6 To solve this system, we can solve for x, and then substitute your solution for x into one of the original equations and solve for y. WHEN TO SOLVE USING SUBSTITUTION: