1. **State the problem:** Solve the simultaneous equation \( \log_3(2x + y) = 2 \). 2. **Recall the logarithm definition:** \( \log_b(a) = c \) means \( b^c = a \). 3. **Apply the definition:** From \( \log_3(2x + y) = 2 \), we get $$ 2x + y = 3^2 $$ 4. **Simplify:** $$ 2x + y = 9 $$ 5. **Interpretation:** This is a linear equation in two variables. Without a second equation, the solution is all pairs \((x,y)\) satisfying \( y = 9 - 2x \). 6. **Conclusion:** The solution set is $$ \{(x,y) \mid y = 9 - 2x, x \in \mathbb{R} \} $$ This represents infinitely many solutions along the line defined by \( y = 9 - 2x \).