It would be C.88-x and there are 36 black keys on an 88 key piano
Answers:

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Work Shown:


P = perimeter

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A = area

The value of
is 
Explanation:
Given that
and 
<u>The value of </u>
<u>:</u>
The value of
can be determined by substituting x = 5 in the functions f(x) and g(x) and then dividing the terms, we get, the value of 
Thus, we have,

Substituting the value of x = 5 in the functions f(x) and g(x), we get,

Simplifying the terms, we have,

Adding the terms in numerator, we have,

Thus, the value of
is 
Think of it as a subtraction problem.
-3x -4y = -1
3x - y = -4
_________
0x -5y = -5
y = -5/-5 = 1
Plug 1 in for y in either of the equations
3x -1 = -4
3x = -3
x = -1
Answer: (-1, 1)