If you have the equation
c(s) + y(g) --> 3 b(g)
and you add a large amount of c, will it speed up the reaction or slow it down?

Assuming the conditions of the reaction are maintained and appropriate for the reaction to still occur, the reaction rate can be affected by increasing the concentration of the reagents used in a reaction. It will speed it up.

The teacher is mostly talking about the distillation of a mixture