Answer:
[tex]a=2K-b[/tex]
Step-by-step explanation:
[tex]K=\frac{a+b}{2}[/tex]
Switch sides:
[tex]\frac{a+b}{2}=K[/tex]
Multiply both sides by 2:
[tex]\frac{2\left(a+b\right)}{2}=2K[/tex]
[tex]a+b=2K[/tex]
Subtract b from both sides:
[tex]a+b-b=2K-b[/tex]
[tex]a=2K-b[/tex]
