Tickets numbered 1 to 50 are mixed and one ticket is drawn at random. Find the probability that the ticket drawn has a number which is a multiple of 4 or 7?

S = {1, 2, 3, ........, 49, 50}
E = {4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 7, 14, 21, 35, 42, 49}
$$\eqalign{ & n\left( S \right) = 50 \cr & n\left( E \right) = 18 \cr & P\left( E \right) = \frac{{n\left( E \right)}}{{n\left( S \right)}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{18}}{{50}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{9}{{25}} \cr} $$