Algebra-1

Question Analysis
This question assesses the student's ability to solve a system of linear equations using the substitution or elimination method. The goal is to find the value of .

Key Concept Explanation
The key concept here is the use of either the substitution or elimination method to solve for one variable and then substitute it back to find the other variable.

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