a)

$2\left(5a-3\right)-a-4\left(3a-2\right)=0$

$10a-6-a-12a+8=0$

$-3a+2=0$

$-3a=-2$

$a=\frac{2}{3}$

b) 

$2b-\left(1-b\right)=11-b$

$2b-1+b=11-b$