If every 10 minutes 3 buses leave then over a course of 60 minutes (1 hour ) 18 buses would leave
The "successful" region has half the size of the whole triangle, so by similar triangles, the probability that the area of triangle XYD is at most 12 is 1/4.
0.25 is a demimal
the one to the right of that is a ratio
the one under that is equivalent fractions
the one the right of equivalent fractions is simplest form
