The current in a 51 resistor is 0.14 A. This resistor is in series with a 28 resistor, and the series combination is connected across a battery. What is the battery voltage?

Answer 1

R1 = 51 Ohms.
R2 = 28 Ohms.

Vb = V1 + V2 = I*R1 + I*R2,
Vb = 0.14*51 + 0.14*28,
Vb = 7.14 + 3.92 = 11.06 Volts.

Answer 2

Even easier way:
Series R=R1+R2
V=RxI
79x.14=11.06