To find the price that maximizes Raquel's revenue represented by the quadratic equation:
\[ y = -0.75x^2 + 24x \]
we need to determine the vertex of this parabola. The general form of a quadratic equation is given by:
\[ y = ax^2 + bx + c \]
where \(a = -0.75\), \(b = 24\), and \(c = 0\). The x-coordinate of the vertex, which gives the maximum value of the function when \(a < 0\), can be found using the formula:
\[ x = -\frac{b}{2a} \]
Substituting the values of \(a\) and \(b\):
\[ x = -\frac{24}{2 \cdot -0.75} \]
Calculating the denominator:
\[ 2 \cdot -0.75 = -1.5 \]
Then,
\[ x = -\frac{24}{-1.5} = \frac{24}{1.5} = 16 \]
So, the price \(x\) that maximizes the revenue \(y\) is \( \boxed{16} \).
To find the maximum revenue, substituting \(x = 16\) back into the revenue equation:
\[ y = -0.75(16)^2 + 24(16) \]
Calculating \(16^2\):
\[ 16^2 = 256 \]
Now substitute this in:
\[ y = -0.75(256) + 24(16) \] \[ = -192 + 384 \] \[ = 192 \]
Thus, the maximum revenue is \(192\) when the price of the hair clip is set at \( \boxed{16} \).