1. **Restate step 5:** We substitute the expression for $y$ from step 4 into the second congruence. 2. From step 4, we have: $$y \equiv 1 - 2x \pmod{6}$$ 3. The second congruence is: $$x + 3y \equiv 3 \pmod{6}$$ 4. Substitute $y$ into this: $$x + 3(1 - 2x) \equiv 3 \pmod{6}$$ 5. Distribute the 3: $$x + 3 - 6x \equiv 3 \pmod{6}$$ 6. Combine like terms: $$-5x + 3 \equiv 3 \pmod{6}$$ This shows how we replaced $y$ with $1 - 2x$ and simplified the expression step-by-step to get the congruence involving only $x$.