kutulu

Why mesh analysis?

I just took the parallel circuit and found it's equivalent resistance:

1/Req = 1/R1 + 1/R2 = 1/4 + 1/8
Req = 2.667

Now you have two resistors in series, so add them up:
R = 4.667

With V = iR, i=V/R = 42/4.667 = 9