The expression 12 - y represents the number of dogs not yellow, derived from the total of 12 dogs at obedience class, with y being the yellow ones. With 5 yellow dogs, 7 dogs are not yellow (12 - 5 = 7).
Sure, here is an expression that shows the number of dogs that are not yellow:
12 - y
This expression is based on the fact that there are a total of 12 dogs at obedience class, and y of them are yellow. Therefore, the remaining 12 - y dogs are not yellow.
In this case, there are 5 yellow dogs, so the expression would be:
12 - 5 = 7
Therefore, there are 7 dogs that are not yellow.