When is somehting transitive property and when is it substituion?

The transitive property is when a = b, and b = c, so a = c. For instance, if x*3 were equal to y*4, which is equal to c*5, x*3 = c*5. Substitution is a bit different, as you're substituting one number for another. So let's say that x*5 is equal to y. In the equation y = 9 * z, x*5 could be substituted for y giving us x*5 = 9*z.