Question

0,77x-2x+13=-13+0,77x

Answer 1

1. (77//100)*x-2*x+13+13-0.77*x=0
2. -(123//100)*x+13+13-0.77*x=0
3. -(123//100)*x+26-0.77*x=0
4. -(123//100)*x+26-(77//100)*x=0
5. -2*x+26=0
Решаем относительно x:
 x=-(-26)/2=26/2=13.