Solution 1:

Applying Current Law at node A for the given circuit we get

10A=6A + I

Therfore I=10A - 6A= 4A

Solution 2:

The total voltage for the above series circuit is V=1v+4v+16v+9v= 30v

Therefore the above circuit can be drawn as following circuit

By using ohm's Law the current in the circuit I=V/R=30/100=0.3 A

Solution 3:

The above circuit is same as