How to simplify a product

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9

According to the 2008 u.s. census, california had a population of approximately 4 × 10^7 people and florida had a population of approximately 2 × 10^7 people. which of the following is true? a. the population of california was approximately two times the population of florida. b. the population of florida was approximately twenty times the population of california. c. the population of florida was approximately two times the population of california. d. the population of california was approximately twenty times the population of florida.

The tree filled 3/4 of a cup in 1/2 and hour at what rate does syurup flow from the tree