how to calculate

20.0 0 R 30.0 0 R 18.0 0 8.00 0 200.0 V 20.0 V X 5.00 A In the circuit shown, the current in the 20.0 V battery is 5.00 A in the direction shown and the voltage across the 8.00 Q resistor is 15.0 V, with the lower end of the resistor at the higher potential. Find (a) emf (including its polarity ) of the battery x (b) current, I through the 200.0 V battery (including its direction); (c) resistance, R