← Day 6
UNIT 5 / 8 · LESSON 2 / 4 · 25 MINUTES

Solve two relationships together

A system’s solution makes both equations true. Elimination or substitution turns two unknowns into one.

01 / THE METHOD

Make it repeatable

  1. Align equations by variable.
  2. Choose substitution when a variable is isolated; choose elimination when coefficients match.
  3. Solve one variable and back-substitute.
  4. Check both original equations.
02 / WORKED EXAMPLE

Watch the method in action

x + y = 11 and x − y = 3.
  1. Add equations: 2x = 14.
  2. So x = 7.
  3. Use x + y = 11 to get y = 4.

(7, 4) satisfies both equations.

03 / QUICK CHECK

Try it yourself

What is x?

04 / PRACTISE AND CHECK

Apply the method to real questions

Start with guided questions and feedback. Then take a fresh independent set without hints. Reach at least 80% on that set to record this lesson.

Pass the quick check above to unlock practice.