An electronic device operates at 20 V and 0.5 A. The power adapter for the device contains a transformer with 300 turns in its primary coil that is used to convert 120 V of household
electricity to the proper voltage.
a. How many turns must the secondary coil have?
b. How much current is in the primary? Need help!

Lx bxh

Ohm's law tells you that i = v/r where v is equivalent voltage and r is equivalent resistance of the circuit
since all circuits have the same voltage, your question is really asking which circuit has the lowest total resistance, since the lower the resistance, the higher the current
circuit a has a resistance of 5 ohms; circuit c is in series so has a resistance of 10 ohms; circuit b is in parallel and therefore has a resistance of 2.5 ohms (review your notes on adding resistances in parallel and series); therefore b has the highest current

What the heck r u talkin bout? ?