Algebra-1

Question Analysis
This question tests the student's ability to apply the substitution method to solve a system of linear equations. The system is given with one equation already in the form , making it straightforward to substitute and solve for .

Key Concept Explanation
The substitution method involves expressing one variable in terms of the other and then substituting this expression into the other equation to eliminate one of the variables.

Step-by-step Solution
1. Start with the given system of equations:
2. Substitute into the first equation:
3. Simplify the equation: