Final answer:
The unit rate between the blackboard and the poster is 1.5 yards per square yard.
Step-by-step explanation:
The unit rate in this context can be calculated by dividing the area of the blackboard by the area of the poster. In this case, the unit rate would be 12 square yards / 8 square yards = 1.5 yards per square yard.
The unit rate represents the ratio between the areas of the blackboard and the poster. It means that for every square yard of the blackboard, there are 1.5 yards of the poster.
There is only one unit rate that can be calculated in this scenario, as we are comparing the area of the blackboard to the area of the poster.