Test how smart you are

A. The length of a rectangle is 9 centimeters more than half the width. Find the length if the perimeter is 60 centimeters.

B.

A box of thoughts I am
Many I may hold.
Locked I can be,
To hide them away
Until the time is told.

Memory, memory, memory I keep
Tell yours to me
I'll save it; I won't peep
A word about it
Unless that is your wish.
Yet, beware, and do not feed me too much,
For not only stop working will I,
But I may also crash.

Believe it,
It's true
Although hard to believe
For so much information I keep
Yet, organized I can be
If organization is what you seek.
WHAT AM I