If the equation is

then rewrite the equation as

Divide boths sides by 7:

Since
, we can factorize this as

Now solve for <em>x </em>:



where <em>n</em> is any integer.
If you meant sin(2<em>x</em>) instead, I'm not sure there's a simple way to get a solution...
F(x) = -3x + 7
y = -3x + 7
x = -3y + 7
-3y + 7 = x
-3y = x - 7
y = -1/3x + 7/3
f^-1(x) = -1/3x + 7/3
Answer: In math a mean is the simple mathematical average of a set of two or more numbers.