Question

What is the speed of light with N=1.33

Answer 1

If the refractive index of some substance is  1.33, then
the speed of light in that substance is
                  
               (speed of light in vacuum) / (1.33)  = 

                         (299,792,458 m/s) / (1.33)  =  225,407,863 m/s

Answer 2

$v=2.25` 10^{8} \frac{m}{s}$
N=1.33 being the Index of Refraction of a material and $c=3.0` 10^{8} \frac{m}{s}$ the speed of light in vacuum you get:
$v= \frac{c}{N}= \frac{3.0 10^{8} }{1.33}=2.25` 10^{8} \frac{m}{s}$ speed of light in that material.