12 Ω resistor in parallel 6 Ω12 * 6/(12+6) = 4 Ω.

The resistance of the whole circuit is 1+2+4 = 7ω.

For the current on 1ω, resistors 3 and 6 are connected in parallel, and resistors 12 and 6 are connected in parallel.

=2 1 /7=3(A)

3 Ω and 6 Ω are connected in parallel, and the current flowing through 3 =3*6/(3+6)=2(A).

12 Ω and 6 Ω are connected in parallel, and the current flowing through12 =3*6/( 12+6)= 1(A).

therefore

I=2- 1= 1(A)