Answer:
[tex]x = 2a - y[/tex]
Step-by-step explanation:
[tex]a = \frac{1}{2} (x + y) \\ a \times 2 = \frac{1}{2} (x + y) \times 2 \\ 2a = x + y \\ 2a - y = x \\ x = 2a - y[/tex]
