Simplify the expression [[$ \displaystyle\frac {3a^2} {a + b} \cdot \displaystyle\frac {3a + 3b} {a^7b} \cdot (a^2)^3 $]] and calculate its value when [[$ a = 2 $]] ja [[$ b = -1 $]]. (Source: Entrance exam for engineering education, spring 1997)

Take a picture of your solution and return it to the submission folder.

Answer: The simplified expression is and the value of the expression is , when [[$ a = 2 $]] and [[$ b = -1 $]].