Answer:
5.41 volts
Step-by-step explanation:
You want the voltage across the 15Ω resistor that is in series with the parallel combination of 20Ω and 35Ω in a circuit powered by a 10V source.
Parallel resistance
The parallel combination of the 20Ω and 35Ω resistors has a value of ...
(20)(35)/(20 +35) = 140/11 ohms
Voltage drop
The voltage across the 15Ω resistor is then ...
10(15/(15+140/11)) = 330/61 = 5 25/61 ≈ 5.41 . . . . volts
The voltage across the 15Ω resistor is about 5.41 volts.