a 40.0 ohm resistor and a 90.0 ohm resistor are connected in parallel, and the combination is connected across a 120 V dc line. A)what is the resistance of the parallel combination. B)what is the total current through the parallel combination. C)what is the current through each resistor?

Answer 1

C) is perhaps the easiest part. Both of the two resistors have the full 120 V applied.
The current through the 40 ohm resistor is 120/40 = 3.0 A. The current through the 90 ohm resistor is
120/90 = 1.33 A

For B), just add the currents going through each resistor. 3.00 + 1.33 = ?

For A) you could divide the 120 V by the total current of B.
OR, you could use the formula 1/R = 1/40 + 1/90 = 9/360 + 4/360 = 13/360
R = 360/13