Help me please I’m confused.

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

The scatter plot shows the number of animal cells clara examined in a laboratory in different months: plot ordered pairs 1, 20 and 2, 60 and 3,100 and 4, 140 and 5, 180 what is the approximate predicted number of animal cells clara examined in the 9th month?

Intro biblioteca sunt 462 de carti cu 198 mai putine enciclipedii si cu 47 mai multe dictionare decat enciclopedii cate enciclopedii sunt in biblioteca