<u>Answer</u>:
c = 9
<u>Explanation</u>:
given: f(x)=3x-7
<em>if f(c) =20</em>
To solve this replace x with c and then y is 20.
<u>Solve</u>:
3c - 7 = 20
3c = 27
c = 27 ÷ 3
c = 9
Answer: Choice D 
Reason:
Exponential functions have the variable in the exponent.
Choice A is a polynomial, which means we can rule it out. Choice B is a log function, so we can rule it out also.
Choice C is a rational function because it is a ratio of two polynomials. This rules out choice C.
Choice D is the only function with the variable in the exponent. That is assuming you meant to say
instead of 
Let

be the identity matrix. Then pick whatever matrix you like for

.
The answer to the question is b.4in