Given
Three 7 ohm resistor are in series.
The battery is V=10V
To find
The equivalent resistance
Explanation
When the resistance are in series then the resistance are added to find its equivalent.
Thus the equivalent resistance is:

Conclusion
The equivalent resistance is 21 ohm
Answer: True
Explanation:
Pencils indeed should not be used as tools when working inside a computer because it is made of Lead.
Lead is a conductor of electricity and as such if it is left inside the computer at even miniscule quantities, it can redirect electricity and damage components in the process.
If one wants to work inside a computer, it is best to use tools like tweezers and needle-nose pliers.