Modulus of a Complex Number

Consider the complex number defined as:

$$ z = 3 - 4i $$

where $i$ is the imaginary unit. Calculate the modulus of the complex number $z$. The modulus is defined as:

$$ |z| = ext{sqrt}(a^2 + b^2) $$

where $z = a + bi$. Provide your answer as a simplified fraction and as a decimal.