Answer:unknown resistance=12.6ohms
Explanation:
Known resistance(r)=16ohms
Unknown resistance(r)=a
Voltage(v)=12V
Current(I)=0.42A
Total resistance in series connection is r=16+a
From ohms law v=I x r
12=0.42 x (16 + a)
Divide both sides by 0.42
12 ➗ 0.42=(0.42x(16+a)) ➗ 0.42
28.6=16+a
a=28.6-16
a=12.6ohms